I have sprayed latex without thinning, works great but does gum up after a while of spraying. I find it depends on the color that you are spraying that will gum up fast or with other colors it take longer to gum up. I have also used Floetrol but this I find leaves a dull finish, if using a high gloss finish paint.

I did not seal my plane because I have heard that the Poly Urethane will over time turn white to a yellowish white color. One added benefit with latex that its cheap and will be fuel proof for gas planes.