After much research I'm starting to lean away from spray foam. Spray kits run around $1/sf for 1" thick, or $1.50 for 1-1/2" thick. I was able to cut polyiso to tightly fit the curved spaces. It runs $10 for a 4' x 8' sheet or $.31/sf or $.94/sf.
The R factors are the same between the 2.
Some good info on why spray foam is not good inside "metal boxes":