I never use less than 6 ml concentrate per 135-36/120 roll. In most cases, 5 ml concentrate per roll probably will work fine, but if you happen to have a bunch of rolls that will end up being quite dense (think high-key portraits in the snow) you may end up exhausting the developer before development is complete.
By the way, the 6 ml per roll calculation is based on Kodak's capacity recommendations (and a little math).
Also, the 6 ml per roll is based on 135-36 rolls, so if your rolls are shorter, the calculations change.
As for stand and semi-stand developing:
1) I don't use it;
2) One of the reasons to use it is to benefit from compensating effects, which most often result when developer does exhaust locally - so the capacity issues are probably made more complex; and
3) I don't recommend doing it, unless and until you are experienced with regular developing.
I wish you good luck, and hope this helps.