That you have to take over a prototype and that you only get 0.6% is a warning sign. You will doing a cofounders job and should get a much bigger share. Even i

That you have to take over a prototype and that you only get 0.6% is a warning sign. You will doing a cofounders job and should get a much bigger share. Even if you negotiate a bigger share now, it would not matter as they have already shown how much they value the technical part of the company.