Revised Charity Tournament Blinds

I had to drop the levels to 25 minutes. Just too long with 30 minute blinds. I softened the transition before the first break and I tried to soften the transition between levels 9-11 (per OhCaptain suggestion. A good one, by the way.) Any suggestions? I am open. 1500 starting chips with 500 add on at the beginning only. most people will start with 2000 and right now we are expecting 80-85 players. We want 6 hours of play.