I run Master so 50# is normal for me. I put 5# each under the front wings of the seat and a 10# curved diver’s weight in the middle of front of seat. I put a 5# on each side and the rest I place on the back of the seat. When I’m feeling anal, I put a 3/4″ washer between the seat and the weight, which keeps the contact to the seat down to a minimum. My thinking is that clamping the entire surface of the weight to the seat will stiffen it, especially with so many weights.
I’ve also removed two 5# from the rear of the seat and placed them on the left and right rear corners of the belly pan. (You do need to watch the F/R balance) This might be worth it because it lowers the polar moment of inertia and improves the responsive of the kart during turn in.