lemme give my 2 lincoln heads a shot here...
foist, I agree with you that there should be that 3 day rule before joining the chart. But I think you should be able to add those days back in at some point, like on Day 28 they can automatically jump to day 31 and get in the month, by resetting their start date.
second, some people have had tremendous chizuk and incentive from the 90 day count, while others have felt it too big of a burden, and their anxiety builds until they crash. We need to do something to help those who find the counting defeats their purpose. Maybe it's cuz too many people are counting on them, it's embarrassing to let others down, but it doesn't defray the urge, either. Perhaps a different (additional) system, where they can register a start date that stays hidden, just shows their name as a participant. Then they work day by day, AND NOT COUNT OR REGISTER THEIR CLEAN DAYS until, say, the end of 2 weeks or a month. The chart could display it in a way that no one knows which date one missed. This chart would ONLY register cumulative clean days, and a person wouldn't have to register a fall at all, just the total clean days each week.
The goal is to give those few who need it a less anxiety filled, more positive approach of rewarding them for cumulative days, not just consecutive. And we can make just as big a hooplah about those milestones, so they do not have to feel like second-class citizens. This could be a preliminary system of choice, and then they can go onto the 90 day chart when they feel they are ready, and get some kind of recognition for the cumulative days there as well.
Oh, and Guard, while you're creating your budget for the mega-bucks days soon to come, please include some SERIOUS rewards for milestones besides revolving graphic crowns. Seforim, Gift Cards redeemable at fine Kosher Restaurants, and All Day Movie Passes, to name just a few...