OK, after talking to Steve Tillett, first I must say he was unbelievably available to assist me, I was told that the right seat mount is usually left untouched and the left seat offset is there on purpose to balance the weight of the engine that's on the right side of the kart. He also told me that if I want to pray that seat stays apart to make room for the larger seat then a simple car jack does the job gently and accurately.
Problem solved
Problem solved