I fitted mine yesterday, and must say I am disappointed. I was hoping to be able to sit further back, in the middle where the GTS seat has its bloody hump. But I found that while the mono has its hump a couple of centimeters further back, the hump is higher, and the net result is the same.
I have now modified it by stuffing bits of cloth through the round hole underneath, and adding to the padding of the central area. Makes the seat a bit stiffer and slightly higher, but a lot more comfortable. Should have tried that with the original seat before spending a lot of money.
I wish Piaggio had produced a flat dual seat for the GTS like they did for the PX and earlier models
But the mono saddle sure looks nice!