Jonjay,
In regards to the corrosion protection, one only need to read the data sheet for the wash coating Vans applies. It states, as I recall, it should not be used for corrosion protection. My only point is that Vans could have selected a much better product at very little difference in cost, and saved a lot of us a lot of time.
I really don't care how many production spam cans are out there flying without any protection. My current 25 year old hangered Piper does not have it and I can already see the start of discoloration in the wings which was not there 20 years ago. In 1980 it was a Piper option to have the interior panels treated, unfortunately the guy who owned the aircraft prior to me chose not to pay for the option.
In regards to the RV-10, when I sink almost $200K and 2 years into an airplane, I would like to think that it will have the best solution possible for corrosion protection. Most who are building the slow kits are using the two part epoxy chromates which accomplish this to a much greater extent than a wash primer.
In regards to the thickness of the coating, I understand the data sheet does indeed specify a very thin layer for use of the product as an undercoat layer, but there are a lot of areas that will never get a finish coat that will benefit from a thicker coating. By "thicker" I mean covering the underlying material sufficiently that it appears a consistent green. I personally have not seen any issues of pealing. I would guess if it was put on real thick there could be issues. Like I stated, I have not seen this peeling issue. It seems once this stuff is put on it is extremely durable.