I tested the change in output before I went ahead. It was not measurable with my voltmeter. The reason is that there is no air between the gelcoat and the solar cell. If there had been, it would have created specular reflection and a loss. However, the addition of too much blue pearl did lower the output a bit, I have yet to measure how much.
In time won't the gel coat become scuffed and scratched? You'd have to be careful of what cleaners you use. I'd also worry about someone dropping anything heavy on the decks.
Sure hope you report back in a few yrs as to how it works out.