adding in my experience on my 22 GT. I bought it more for long term ride comfort thinking it would shift more weight to my glutes and away from my thighs.
Installed the 8mm one. Had a real bear of a time getting the gas tank bolts to fit ( tank was probably 1/3 full of gas, my mistake). Just came back from a 5.25hr ride (with a 3 min break, 60 min break, and 3 min break), with heavy cross winds. Definitely more comfortable and I think may be what I need to do back-to-back 6-7 hour rides. I may not even need the comfort seat I ordered from the UK.