I'd aim for 10's in all guard skills as a baseline. That caps the star potential guys (depending on their secondaries) then you can tweak the higher potential guys as you see fit. I think guys with 10's across the board in guard skills would be great in V and IV and serviceable backups into D.III especia
All 10s shouldn't cap a star unless it's a very low sublevel of star potential and they've got strong or higher rebounding (and even then, I don't know if that would be a cap since we don't know how much JR has dropped).
I'd say that a very good target would be 14 OD, 8JR, and 10+ in the other guard skills. I've still got a few star potential guys with those skills who play for me in II.