My major concern with moving the pillar forward would not be putting stress on the hull, but reducing the clearance between the bulk head and the leading edge of the pillar and therefore increasing the risk of foot entrapment.
I weigh in just under 140lbs & am about 5' 10". I moved the seat about an inch. I put alot of kit in the back of my boat and needed to move it that far. If I didn't carry loads of stuff 1/2 an inch would have been fine for me.
I'd try it at 1/2 an inch first. I think if you move it forward an inch you weight will be too far forward. While this wont have any major effect on nornal paddling, it will on the steep. When tuck forward when running drops you will end up planting the rocker on landing, and will therefore not be on the surface in control. You might also have your weight to far forward to punch holes as the rocker wont skip through the foam pile, but slow you down and stall the boat.