I've seen your work with the elastomer "damper", and had an idea:
Given how hard you say it is, and how you bolted it to the frame, I suspect it does not really work as intended except for really fine vibrations perhaps (and since your tires already take care of them, I doubt it works at all).
There are special vibration damping/isolating materials out there, with pretty well-documented parameters, like this, for instance.
https://www.getzner.com/en/solutions/materials/sylomer/
http://www.christianberner.se/$-1/file/sylomer-sr.pdf
(also, there there is sylomer HD with much better damping properties, but much less info is available about it)
You can calculate the required type and thickness based on your area of contact and your weight. I bet it would result in MUCH superior vibration damping and isolation. You can glue a few layers together, and than use your velcro trick you did with Silvio to attach slabs of material to the frame and the seat without bolting them. (
Being dirt-poor (just frameset alone would cost me half of my YEARLY wages) I cannot afford Vendetta + shipping, but I'll surely ask a local welder to make something similar, kinda like mhelander's 'diy vendetta' from BROL, but with more tire clearance (will use fatter Schwalbe marathon tires) and surely will use your trick with 'seat mounting on velcro with damping".
Our roads need all the damping one can get and than some.