Seat placement


I have a slack sp7. I'm a bigger guy and have an xxl seat. I know the top needs to be 8-10 inches off the axle but when I put the seat in it sits right up against the side plate on the motor (flatehead). It also looks as though the left side of the seat is a touch higher then the right side. Any real adjustment will force me to cut the seat. Any thoughts or insight would be appreciated