When I covered the wing fillet on my Mustang, I started in the rear and ironed down strips of chrome Monocote length-wise along the fillet. I started with longer/wider strips in the rear of the fillet, and shorter/narrower strips as I went around the curve in the front of the wing. It created a shingle effect, and the borders between the strips weren't too prominent. You're trying to cover a concave section combined with a convex curve, and the longer/wider the piece of covering, the less it will tolerate a more pronounced compount curve. You have to judge the length of the strip by the amount of "bend" you're dealing with. Make the strips on the outside edge about 1/2" wider than is needed, then pull them around the bottow of the fillet and iron them down.

One thing that helped was that I was able to borrow a friends trim sealing iron. It's got a rounded bottom on the shoe, which really helps glue the Monocote to the fillet. Then I used a heat gun and an OveGlove to really press down the covering. I think it might actually be easier to cover a compound curve with Ultracote because I think it shrinks better, but adhesion to the curve might suffer because I think Monocote sticks better. But that's just me, and I don't want to ignite that whole Monocote/Ultracot argument again.

I built the fillets from balsa strips, then rough sanded them to contour and used BalsaRite to smooth out the curves. If I had it to do over, I think I'd rough in the large areas with balsa, then use some sort of epoxy/microballon mixture to smooth it out, going heavy on the microballoons so it's easier to sand. The problem with the BalsaRite was that it would melt under the heat from the trim iron if I pressed too hard.

Good luck with it.

Fred