RB-300:help ;I think I'm wacked

The reason that you don't need to do the mods on the RB 600,900,1000 is that you can get the OL Silver Tonearm for $750, that will be a way better arm than any of the Regas, before or after modification. Why buy an arm that costs more and won't do as well? The OL arms use Rega bases, and fit right into the Rega arm hole. The 250 and 300 are cheap enough to be good candidates for mods, and not cost too much after you're done. Anything over $750 is a wrong move. If you plan to spend that much, buy the OL Silver Tonearm. It has the better bearings, a widened bearing yoke distance, and a totally different armtube/headshell. This is better than any modded Rega.

You have to be careful when doing mods, that you don't spend more than the amount where you can do better by buying something else.

No, I haven't listened to the new 1000 yet. I expect it would be a very good arm. From what I can see of it on the website, it appears to continue the Rega practice of refinements on the RB300 theme. It still has the spring VTF adjuster. All of these arms, including the OL arms still need the Expressimo Heavyweight. I was shocked at the improvement I got on my OL Silver with the Heavyweight. IMO, this mod is not optional. It should be standard on all these arms.

I am beginning to see. I checked out some webs. It would appear that the reason the rb-250 would end up being better after mods is because it is coupled to the base on both ends of the vertical bearings, where the arms built with the springs are coupled on on side only; the are not coupled where the spring is attached(except by the spring itself).
Furthermore, it seems the reason rb-300's and above are better "out of the box" is they use better materiels on the end stubs, where the rb-250 uses plastic.
What I can see is the importance of the end stub & counterweight, as this is a place where resonences can reflect and the mass is significant as to compete or interfere with the mechanical grounding of the arm.
What I don't see is how couplng the counterweight rigidly with a set screw would make a improvement, or coupling the end stub solidly, for that matter. I understand that the origin mod is supposed to be solid with "less" coupling. The expressimo end stub appears to be the same as a stock one, with the exception of having a allen screw to torque it down, I can't see how the origin is attatched.
Question; is there something about a rigid mount to the end stub/counterweight assembly that makes a tonearm perform better? (as opposed, for instance, to coupled with some sort of damping?)
Question 2; is there something to the "torque" involved that makes the end stub behave differently, as to perhaps be better than further or appropriate "decoupling" of the whole assembly?
Has anyone done any exploring with the attatchment of the counterweight, either before or after the mods? Or with other tonearms?
I am sure there is something to this that can help us build a better tonearm. I am especailly curious as it appears that there is knowledge in this area that I may have been previously unaware existed.

I prefer the OL method of coupling the end stub to the arm. This coupling method actually causes a tuned de-coupling of the vibrations which may excite the end stub and counterweight. By doing this, the overall amplitude of the vibrations is lessened because the high mass items are de-coupled from the tube/bearing. It also allows the rigid coupling of the counterweight to the stub, so they act as a single mass, instead of letting the heavy counterweight vibrate on the rubber ring/plastic stub. This changes the basic design of the Rega arm, which uses direct coupling of the stub, and de-coupling of the counterweight via the rubber ring. Any time that something as heavy as the counterweight is allowed to get moving, it is going to transfer large amounts of that movement to the surrounding parts. This is why the rigid attachment, tuned de-coupling, and coupled counterweight/end stub is a good combination. As has been said before, "Rega made one of the best arms in the world, when they made the 250. They just didn't finish it."
The torque of the stub is importand to the tuning of the coupling. It changes the resonance characteristic of the coupling. The same is true with the tightness of the main nut that holds the arm base to the plinth. Too tight sounds dead, too loose allows information loss, and unstable mounting. There is a very musical "moderate tightness" that this nut has to be tightened to, by ear. It never needs to be more than "finger tight". No wrench is needed.
I have tried all kinds of counterweights and attaching methods at all different stages of mods. The rubber ring method is crap at any stage. However, interestingly enough, a pair of rubber o-rings around the circumference of the counterweight works well at any stage of mod for a 300. You can try this out with a rubber band wrapped around the counterweight, as an experiment. This will work, but the o-rings are just as good and look a hell of alot more acceptable. And they are only about 75 cents each. The OL end stub with the Expressimo Heavyweight counterweight is the best combo, at any stage, and will give you the most increase of any mod you can do to that arm. If you are laughing out loud now, just wait till you do this combo to your arm. You will be laughing hysterically, that you thought you were doing great before. The total will be under $200, and is worth every penny of it. Since you already have re-wired the arm, this end stub and Heavyweight is all you need to take that arm as high as it can go. A little damping here and there, depending on the cartridge used, and you have an arm that really never needs to be traded-in, unless you are "going for broke" and want to spend big bucks. And you would need a really great table to reap the benefits of any more arm than a fully modified Rega. I can't remember what table you have, but if it is not a $5k plus TT(or equivalent performance, like a Teres) then you have no need for any more tonearm than you've got. Unless you want to get a 250 to do the mods to instead. If it were me, and I already had a re-wired 300, I would just mod it up and be done with it.