Originally Posted by momoese
What about a pneumatic metal shear? You have air?
I had thought of that and, yes, I've got 3 air compressors (220v, big PTO driven, and smaller Honda gas driven), but cutting the gable tops will require cutting through lots of ridges that stand one inch tall and it's pretty hard to cut a straight line when going over ridges at an angle.
I found some pretty good advice here:
Cutting Steel Roofing
A nibble is a good option but one poster mentioned that for straight cuts there's a sheet metal blade for circular saws that works great.