Before you give up on your Gunfighter, try sitting closer to the tank, further up to the front of the seat for a while.
I found a sweet spot up there after trying for a couple of years to sit back in the seat, even up onto the rise to the pillion even. Sitting closer to the tank made a big difference to me, and I ride several hundred mile stretches regularly.
When I installed the TRIUMPH Touring Seat, I found the same to be true. I have not tried to push back in the seat since, unless I'm putting my feet on the rear pegs for longer highway runs, and that works very well then.
Don't give up on your stock seat so soon!
