Which one? The one with the larger radius R3/R4 or standard R1/R2?
The wider R3/R4 is 7.9 feet by 5.4 feet.
I would always round up and give yourself a few inches breathing room.
For the standard R1/R2 you want 4 feet wide. I would go with 4x8 at least so you could stretch it out a little. Here is my old 4 laner.
