I have given the Corbin seat a good try out and despite the good reports, it did not suit me, well actually my pillion complained of sliding about on the leather covering.
I thought it felt firm initially but as the miles mounted it was actually quite good, except that I felt that the seat was made for an American butt i.e more room than I needed art the front, pillion comments apart from being to smooth were very complimentary.
Anyway as I have to travel a lot on the twisty roads here in the Picos with a passenger, I will sell it, but probably not to you guys 'cos you're too far away....unless of course you want to pop down and try it out before buying. Cheers