The guy from the spray foam company did explain to me why the difference in R value b/t open and closed is not a significant factor, so I am going with 5" of open cell under the entirety of my roof. Keep in mind that my main concern is radiant heat, not energy efficiency. As for the crawlspace, I'm doing it more to condition the cellar/crawlspace than I am for energy savings. My HVAC runs through my cellar, so I'd like to keep it warmer down there in the winter. It's also important to me to keep out moisture, and hopefully spider crickets. My crawlspace has a dirt floor, so they'll be laying out plastic too. The house is 100 years old, so you can probably imagine how gross the cellar might be.
The company I'm using has been around for over 5 years, and is used exclusively by a well known builder, so I'm comfortable with them.