Cutting kerfs in the rigid foam will allow the panels to conform. I use a sharpened spackling knife to cut or score rigid foam. Works like a champ!
I was at the big box store today, and the R-Tech rigid foam now comes with a reflective metal reflective facer. This is the first time I've seen it. It helps with moisture control. Anyway... back to my dilema...
I noticed the fiberglass batting at 6.5" thickness has an R value of R-13. The rigid foam uses the term "effective R-value". To get close to an R-13, rigid foam needs a thickness approx. 2.5". Trying to figure out if there are any technical advantages of using rigid foam. The fiberglass seems easier to install, other than protecting exposed skin.