I see what you mean (picture if not the best quality) but no, the edge is close to the tire all around.
Even if I had a gap, impossible I could loose the disc. The disc is firmly attached onto the original covers with 4 nylon insert lock nuts and the original covers are of very good quality and holds very well on the wheel. All it could do, in the worst case, is bending the disc (original cover stops halfway between the bolt and the edge of the disc).
As for the pressure, I have to remove the cover to check it. I need a lever because the aluminium is not stiff enough to pull on it and as I said, the cover below holds well to the rim. I would like to have a complete smooth surface. I'll see with time whether it's really inconvenient or not. If yes, I can always bore a hole. But so far my tires holds pressure very effectively (0.1 bar loss every 2-3 months).
With the cover fitted, the 155/80 R13 wheel looks like 155/55 R16.
