The standard 1150 has seperate seats for rider-passenger and I reckon more comfortable than the ADV single seat, which is a bit of a plank unfortunately
Would agree with Bryn.
Joanne insisted that the seat be sorted on our GSA before she would travel any distance on it.
I do believe you can purchase a pillion seat extension for the 1150gsa,not sure from where,or if indeed they are any improvement.
My missus much prefers the twin seat set up, even though I added on the TT seat extender to the adventurer seat. Better shape for the pillion IMO. Also as there's a bit more of a step with the twin seats, she found it harder to nick my bit of the seat.