so... if it is your suspension that is supposed to do the up/down work, technically your car would handle/ride better if the subframe didnt move at all correct? then, what are some options for solid rear subframe bushings? the only ones I found so far after searching are these from TAP auto parts:
whiteline is a hard polymer but still does a better job than the OEM one it looks like...
[ame="https://www.youtube.com/watch?v=IDfJ_zYFPcs#t=134"]BRZ / FT86 / FR-S Whiteline Subframe Lock Out Kit - YouTube[/ame]