Dagger includes outfitting for leg and seat adjustment and the seat itself is very comfortable. The backband is adjustable and provides great support as I rotate my torso during paddling. A great resource are the online videos on the Dagger website that explain out to use the provided padding for outfitting my boat.
The 8.1 does fit me, but I am probably at the top end of height and leg length. I am 6'1 and 190 lbs. My paddling partner is a bit shorter, but heavier and fits the 8.6 Mamba better. I have yet to have the opportunity to paddle above a Class III, but the fall paddling season is here!