Are these R values aged? I use Demilec, and it is 7.2 per inch. I would not recommend spraying foam by putting holes in the wall, and then spraying. Not only do you risk blowing out the wall, but you also risk it not curing properly.
Where are the off-gasses going to go? What if you have lath and plaster, and it overexpands?
As a drywaller and sprayfoam installer, I believe this method is very risky. Especially thin coat plaster. I wouldn't recommend it. Open cell foam is not waterproof, and in my opinion worthless, for the price you pay, anyway. I guess everyone has their own opinion. I'd say your info is misleading. --Jamie L.