Yes it's a tricky balance, probably if we could some absolutely secure escrow we could follow in the footsteps of the original ponzi which paid 150% in a month and a half. large payouts at the end of the term also break cashflows.
We have to ponder over all the possibilities a little.
Instead of hourly payments i suggest daily. Lots of people will be happy with 1% return every day. But many people wont be happy to lock their coins in for 150 days. Its a tricky balance. Maybe you should keep the funds for 14 days, and give 1% each day. on the 14th day pay out 114%?