i also have a lot of work done myself and there are plenty of motivated ppl who would like to join a crypto-business.
I don't believe it's possible to determine if hourly rate is better than a % for any new project, specially when there's no trust.
Lets say that you make a deal for 50-50 split, and the project yields 2BTC profits, why would a developer trust you to hold 1BTC for him?? how would the developer trust you to report the exact profits at first place?? too many ways a % can go wrong when dealing online without legally binding contracts.
If you're willing to pay plain flat price shoot me a PM (on site, or email only, no IM apps) to discuss the deal.