I've got a 6x10 trailer that i run. Unless you only have one machine, get something bigger!
I just bought my Gravely 260Z and it takes up almost the hole trailer by itself. i still manage to get a 50" WB in front of it, half hanging over teh tongue though. I'll see if i can get a picture of it tomorrow.
btw, you can just squeeze a 48" scag wb + 50 gravely WB on a 6x10. both with velkes
Efficiency = Profit