So I've had penguin pro cut rails on my tablet for some time now. Wanting to get even tighter pockets only on the corners. There at 4.25 would 4inch pockets work on a 7ft? I'm for sure doing 4-1/8in next.
4" pockets still have lots of slack. You may want to player better position at first but that's about it. IMO the difficulty comes in if the table is not level-able.