Gelcoat/Duratec Coverage

[76SeaRay]

I didn't quite find an answer to this question in searching here. I see that Gelcoat and Duratec are mixed at 1:1 so having a gallon of gelcoat I need to order a gallon of Duratec. So my question is this. With the mix ratio 1:1 you end up with two gallons of liquid to spray so does that mean you have twice the coverage or does the thinning then require double the amount of coats giving the same coverage as if it was only one gallon? I would guess you need to double the coats for the correct gelcoat coverage or something in between.

Or, can you spray one or two coats of gelcoat without Duratec and then spray a finish coat with Duratec to reduce the cost?

Thanks...