Whoever told you not to either doesn't care about going round corners or is more into long distance comfy cruisers!!
I've spent 5 1/2 hours today making up a pattern roll bar to go on cossie's with the MC2 RACING poly mount, the bar is a 22m adjustable sort(3 points) fits perfect too, anyway back to the point.
I fitted a mc2racing poly mount and the difference is amazing, really does show how shit the std bush is.
I tried this for two months WITHOUT the rear roll bar, on purpose, to compare to the std bush with no roll bar, comapred with std bush the poly takes away 80-90% of the body roll.
Of course with the(new design) roll bar back on there is little if any roll at normal speeds, you do pick up vibration with the poly, but soon forget about it as it's not intrusive, the only odd thing I found was when the tank is at a certain level it makes a bit of a drumming sound at around 50mph 1/2 full, but sure a vibe pad on tank will cure this by tuning it out.
Now with the poly on when you hit a bump you lose 90% of the rear wheel steer effect, the stability is VASTLY improved beyond all recognition, the very slight downside is massively outweighed imo by the benefits, I always ask myself this, if I had to do it again would I, YES it's a no brainer for me.
Currently two std diff mounts sit in a lab in Northampton being anylysed for hardness and other things they do, then as soon as these are back with the new poly mixes, one of each type will be made and tested, these are based on a std mount but pressure injected and slow cured to increase shear strength, so will look almost std, be less than 1/2 the price, and not have any fitting problems or need anything different done.
tabetha