I have an oversized 8 (8.5'). I really like it. On one side (along the long rails, not where you break from) the 5' suggested exists, but it's from where the cushion meets the rail. My table has rails about 6" wide and with this I have about 8-10" total stroke room. I've not had a problem with it, nor has anyone who has played. No walls have been bumped. When you're talking straight, non angled shots across the table you don't really use a 10" stroke while the CB is frozen to the rail. Break shots are about the only shot where people get "wild," and this would only be an issue if you shoot with the CB frozen to the rail, instead of 2 diamonds up in the normal location.
I'd say you will be great with an 8'. Half an inch short on width and an inch short on length shouldn't really be an issue. If you end up having to put the table a bit off center, I'd suggest more room at the foot since there is usually a lot more play down there.