No problem doing on a peaked roof. Just run individual panels on each slope and a ridge cap on top. I'll add some pics with a ridge.
That photo the lathe is 5/4 x 3 (True 1") with R-5 We've also done it with 2x4's & 1.5 in foam. If you use blue-board or some of the high end foam board you can increase a couple of points on the r-value.
We have had homeowners tell us with the 1" foam they have used up to 20% less fuel. I would say the average is probably less but everyone states they notice a difference. Use an Energy Star color and save on cooling costs in the summer as well.
We usually do no more than a 3" overhang. Anything more it looks like your roof is wearing a hat.
Here the basics of the install process.
1. Install lathe on entire perimeter of home.
2. Lathe is run perpendicular to the trusses/rafters. Attached with 3" ring shank nails. 2 at each crossing. We use a piece of the foam as a spacer as we go.
3. Install drip edge on entire perimeter lathe. We use wide faced drip edge & install with roofing nails
4. Remove all roof vents, plum boots etc an install lathe under them. Re-install or use new vents & boots.
5. Install your metal panels using color matched screws with neoprene washers. Screwed to the lathe of course. Screws are installed adjacent to the ribs. At the edges we install screws at every rib.
6. To seal cuts around the vents we fill the corrugation with foam closure strips, screw down all around the vents and apply sealant.
The foam reduces the gap to fill & helps to hold the sealant while it cures.
This takes 3 men 1 long day. Some times day and a half.