I have used this mask (Gerry Davis markets it as the
Wilson New-View Mask) for a little over one season now, and I love it. I have paired it with the new
Wilson "wrap-around" mask pads also sold by Gerry Davis.
Haven't had the cap coming off problem you describe; in my experience, that problem is usually associated with your mask being on too tight. Loosen those straps a little and see if that doesn't cure the problem.