Cafe Press does not mention if the new Scrine caps are roomy enough for an inner layer of tinfoil.
If you shave your head, I find, you can get a much better fit and better protection.
As with anything involving tinfoil protection, two things come to mind: first, proceed with caution and secondly, results will vary, depending upon the particular shape of the head and/or the type of mind control and/or aliens involved.