There's an older barn locally that has just that type of roof (radius). I don't know how they did it, but the metal roof looks like it conforms pretty well. It was just installed last Fall. If I remember, I'll swing by there and take a few pictures of it.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).