Here is a couple of things you may want to try:
1) Pick a set # of reps, say, 30, to do with 225. You can do 17 now, so maybe do 15 on your first set, then rest for less than 60 s, than repeat, and keep track of the number of sets it took to reach 30, than try to beat that next time.
2) If your familiar with board pressing, you may want to rep out with 225, than add a board, rep out, add a board, rep out, etc. (I got this one straight from Jason Ferruggia over at elite fts. in the sport specific section, I actually think he answered this very same question over there not long ago you may want to check it out).