Anyone replace the springs of a Nobsound footer?


I purchased two pairs of Nobsound spring footers to place under my REL S/812 subs.  The front of the sub is much heavier than the rear of the sub, so the two Nobsound footers under the front of the sub, with all seven springs installed, are compressed nearly 90%-95% (rather than the 50% that I understand is optimal).  I’d like to purchase some stiffer springs to see if this will work better.  
Have you purchased any other springs that were different in stiffness than the springs that come with the footers?  If so, where did you find them?

in advance, thanks!

louisl

Under my solid speaker stands  Granite base I use Pads from garage rubber locking pads cut to size 1/2" .. And between my speakers and Stand I use large mouse pad rubber cut to size... Yes in your mind you can spend thousands of dollars for all the footers...And sure some footers look beautiful enough to put in cabinet and look at for art...But that is what makes us audio people chase and talk about product..

Thanks to everyone for your suggestions!  I think I’ll try to add an extra Nobsound to each of the front corners, as suggested by Audfile1 and Carlsbad2.  

Thanks to everyone for your suggestions!  I think I’ll try to add an extra Nobsound to each of the front corners, as suggested by Audfile1 and Carlsbad2.