From my quick tests i found that it takes about 14 prof per PT to make the message in the corner go away. However, i also found that going from 1 PT to 2PT, when i had only 15 prof, didn't seem to make my accuracy worse, it just didn't get better. So why, my character with 10PT and 100 and something prof can't throw war darts or daggers accurately is beyond me.
i don't have the patience to do enough tests to actually figure it out. I wish chadz would tell us how these systems work when he randomly decides to put them in, because they are just annoying as hell untill someone figures them out.