A small follow-up based on last night's game:
Chip denominations worked well. In retrospect would maybe bump up the blues and greens by the next step across the board. Ran into the need to swap chips across the table a few times - nothing serious though)
Biggest issue was level length. 20 mins was just too short. The shorter stacks didn't have much of an opportunity to overcome poor cards. Yeah, the short stack finished 3rd, but it was Nikki and she's a kick-ass tourney player.
Recommendation: Start early, include a dinner break and run 45 or 60 min levels.