The last question first yes the 2 part paint works fine over it.

As for water vs laquer one thing you must know abt me is I used to paint cars and my plane and when i did taxidermy my fish and stuff all with laquers I love laquer paints because of their blending ability so it naturally went over to the poly U.

But realistically I like the laquer based poly U because to me it gives a harder surface and finish. I had a run once and couldnt cut it with 60 or 80 grit sandpaper but when I used 320 wet/dry paper and wet sanded it i found it cut nicely (go figure). with the water i felt it didnt give quite as hard of a finish but still a nice finish. if you were to give your wing 2 or 3 coats of sanding sealer sanding between each coat I dont see a problem using the laquer based there but I would suggest trying it on scrap. Water based seems to take longer to dry is why I dont like it and of course it is burnt into my head water and wood dont mix. There are people who have noticed warpage or raising of the sheeting in places using the water based and otheres who have used sanding sealer or 1 layer of epoxy first to protect the wood then using the water to finish without problems. I dont use foam at all so have never tried it but I would bet a bundle that if your seams were filled and you used sanding sealer you wouldnt have a problem. I think I would just paint some laquer based directly on some foam and see what happens maybe it wont even affect it thus we are needlessly worrying. I have some 2 " beaded foam downstairs I think I will try it on this afternoon and post the results.

Joe