Looking at doing a flash a batt detail for my exterior walls. Northern Iowa climate zone 6. Here’s my thoughts. 2” halo exterra gps outside the wall with a rain screen, 2” spray foam, 3.5” real wool batt giving me a total r of 37. Or instead of 3.5” batt filling the rest of cavity with real wool blow in for a little higher total  r value of 39. Does this sound like a good system? Any thoughts or input would be greatly appreciated. Thanks!!