I used a 23ga x 1 1/2 for sus. the first time I took it and it was plenty big enough , diden't even have to warm the amps first , it did draw a little slower though. I know a couple of guys that use 21ga , I think that is a little overkill though.
but , you could shove a coathanger in your ass and it woulden't hurt that bad if it was sharp enough.