You should be able to string the POG 90 with 33' of string. It has a 14 x 18 pattern doesn't it? Give yourself 6' on the short side with the long string. You might have to be a little creative. If you have enough left over with the short side, string the top cross and tie off. If you want to be safe, just start stringing the crosses down from there and tie off to the previous cross. Or, after the last main on the long side, bring the string down to about the 7th cross and string back toward the top. Then, use the short side and do a starting knot where you left off and string toward the bottom.
Coachrick has a good memory. I have a set of Winn string here and it, indeed, is 22 x 11.