Heres my general understanding / working hypothesis, for what its worth.
As far as I understand it, theres two basic approaches to tweaking boxes (for lack of a better word): mass loading and isolation. Now, I was never 100% sure which role something along the lines of a maple block was intended to serve but I always suspected that it worked best in the mass loading camp. Which role it is capable of serving, however, will depend on the nature of your footer.
An example. Many maple applications employ a spiked footer between the block and the component (either independent or replacing stock footers by physically screwing into the component). In either case, I would assume that by physically coupling the box to a massive wooden block you are fundamentally employing a mass loading application theory being that by increasing the effective mass of the box through the couple, you are making it more resistant to any vibrations due to the increased mass. Following this theory, a screwed-in spike would be more effective than a free-standing spike, but both seek to achieve the same goal.
Now, in contrast, if you employ a footer that seeks to de-couple the box from the maple block, you cannot really be said to be mass loading. Rather, the block is acting as a vibration sink independently of the box, because the box is not coupled to it. On this theory, the purpose of the block would be to increase the efficiency of the isolation footer by decreasing the amount of vibration that reaches the footer coming up from the ground (or whatever else may be beneath it). In such a setup, the maple is acting as an isolation device.
Fundamentally, I do not know which application maple is better for, mass loading or isolation but I have certainly seen it used for either.
Regarding your CDP (which I am not familiar with) it sound like your stock footers are build on an isolation theory as you describe them as a combination of aluminum and something soft, I assume that anything other than a rigid couple is isolation-based. Thus, and heres my theory in application, you are likely using the maple more in an isolation sense than in a mass-loading sense. If your were to switch to rigid spikes between the CDP and the maple, it would change the nature of the application you are using it in to more one of mass loading. Whether that would be beneficial to you or not, I have no idea, but I suspect it would be different.
Now, if you mass load by adding weight to the top of the machine (Ive used those lead-filled leather paperweights), your would not only be mass loading from the top, but you may well be decreasing the isolation characteristics of the stock feet (by increasing the mass they need to support, of course) and therefore shading the useful effectiveness of the maple block more towards mass loading than isolation by decreasing the effectiveness of the stock footers isolation capacity. (I may have lost myself, anyone still with me ?)
It sounds like youve got some serious isolation under the rack, so experimenting with mass loading may be at least interesting to try (and, conversely, dialing up isolation applications something Ill leave alone). But, at least according to my working hypothesis, theres a bunch of ways to get that done, each of which may impact the usefulness of other things you have in play. So, complicated? A working theory? Best of luck.
As far as I understand it, theres two basic approaches to tweaking boxes (for lack of a better word): mass loading and isolation. Now, I was never 100% sure which role something along the lines of a maple block was intended to serve but I always suspected that it worked best in the mass loading camp. Which role it is capable of serving, however, will depend on the nature of your footer.
An example. Many maple applications employ a spiked footer between the block and the component (either independent or replacing stock footers by physically screwing into the component). In either case, I would assume that by physically coupling the box to a massive wooden block you are fundamentally employing a mass loading application theory being that by increasing the effective mass of the box through the couple, you are making it more resistant to any vibrations due to the increased mass. Following this theory, a screwed-in spike would be more effective than a free-standing spike, but both seek to achieve the same goal.
Now, in contrast, if you employ a footer that seeks to de-couple the box from the maple block, you cannot really be said to be mass loading. Rather, the block is acting as a vibration sink independently of the box, because the box is not coupled to it. On this theory, the purpose of the block would be to increase the efficiency of the isolation footer by decreasing the amount of vibration that reaches the footer coming up from the ground (or whatever else may be beneath it). In such a setup, the maple is acting as an isolation device.
Fundamentally, I do not know which application maple is better for, mass loading or isolation but I have certainly seen it used for either.
Regarding your CDP (which I am not familiar with) it sound like your stock footers are build on an isolation theory as you describe them as a combination of aluminum and something soft, I assume that anything other than a rigid couple is isolation-based. Thus, and heres my theory in application, you are likely using the maple more in an isolation sense than in a mass-loading sense. If your were to switch to rigid spikes between the CDP and the maple, it would change the nature of the application you are using it in to more one of mass loading. Whether that would be beneficial to you or not, I have no idea, but I suspect it would be different.
Now, if you mass load by adding weight to the top of the machine (Ive used those lead-filled leather paperweights), your would not only be mass loading from the top, but you may well be decreasing the isolation characteristics of the stock feet (by increasing the mass they need to support, of course) and therefore shading the useful effectiveness of the maple block more towards mass loading than isolation by decreasing the effectiveness of the stock footers isolation capacity. (I may have lost myself, anyone still with me ?)
It sounds like youve got some serious isolation under the rack, so experimenting with mass loading may be at least interesting to try (and, conversely, dialing up isolation applications something Ill leave alone). But, at least according to my working hypothesis, theres a bunch of ways to get that done, each of which may impact the usefulness of other things you have in play. So, complicated? A working theory? Best of luck.