I like both, but one seems to have more of a direct impact than the other..
Poly Trans...mount...seems to solve the problem passively with more effort involved to install than the upper mount...
It would seem more practical to solve the problem directly with an engine mount to stablize the higher outputs as opposed to the poly trans...and with less effort to install.
Eric what was your conclusion on installing the upper Engine mount..? Your website (which I believe itsuggest it actually improved your shifting after this mod.