OK Speed, here's how I see it. The stall angle of any wing is fixed, it won't change. OP reckons he's stalling at too high a speed/height. Just about all model wings stall around 8~9 deg AOA. That's what the stall angle of his wing will be. An Extra is no different than any other model airplane, his wing will stall around that angle. His elevator is getting the wing to that angle, and at landing time, slow speed. The only thing that can change this wings speed of stall is weight. He has a new, heavier engine so his stalling speed is going to be higher than before. Yes, the balance may be forward of what it was, but that won't change the stall angle, it will change elevator sensitivity (feel) and authority, but he is still stalling the model, and I would guess the elevator stick is closer to full up than before. So authority is fine, balance is fine, sensitivity is down. He could increase the sensitivity by moving the balance back, but that won't change the stall angle, or speed, unless he adds weight at the back, in which case stall speed will increase again and the stall will happen even earlier. New engine, heavier airplane, higher stall speed, need to practise landings for the new conditions. You can futz about with the balance and elevator movement, but it won't change the basic problem.
Evan, WB #12.