A formula I've used is to take yourselves out of the equation. Pretend that you are going to hire outsiders to do the design and dev work. Decide how you would

A formula I've used is to take yourselves out of the equation. Pretend that you are going to hire outsiders to do the design and dev work. Decide how you would split the profit, given that you would be doing zero work yourselves. Then bill your time back against the revenue at realistic hourly rates for the qualifications and experience. Finally split the profit as decided above.