Dave,
I do not see any differences in the aircraft.cfg of the Base Pack and the Expansion Pack which could influence the bouncing behaviour. Except for the [fltsim.X] sections above [weight_and_balance] they are identical. I have downloaded both packages from Simviation (and supposedly schulli and Sandra_007, too).
Here are screenshots from the ACM programm showing the contact points from both Packages.
http://www.fsdyn.org/temp/fxp/ta183/contact.html
I worked very carefully loading the respective cfg- files. The Expansion Pack was easily recognizable with the extended choice of paints in the menue.
I cannot detect any difference in the values of Moments of Inertia in the aircraft.cfgs, too.
The third picture is from the aircraft.cfg Sandra_007 has modified. In a post above she reports that the Ta-183 did not bounce anymore and that the aircraft rotates now properly on take-off.
Most essential in my view was, that she moved the main wheel forward close to the CoG. She surely will tell you all other modifications in more detail.
If anybody does not understand my English text I will translate it to German.
Wenn jemand den englischen Text nicht versteht werde ich ihn ins Deutsche übersetzen.
Carl