I just noticed this message board! Fortunately for me, there's an RV window manufacturer just 15 miles from me in Vancouver, WA. They measured and built custom windows (all 5), and installed with a stick-on black neoprene gasketing. They don't leak at all, and the design is very nice - they don't sweat, and they have large drain slits in the frame, instead of the little holes that clog up over time.
As for the curve, they just tightened it all up and it sucked into shape just fine - the curve is really only 3/8" over 4 1/2', so both the FG shell and the aluminum frame gives a little to mate well. Since the front & rear windows are three-section (slider/fixed/slider), there's some flex to it all. I'll post some pix next week when I get it ready for our first trip of the season.
