Thanks guys. Yes I am familiar with the air stop tubes. I read about them on Mooneyspace! That is probably the best, simplest and least expensive solution, although not quite perfect as ideally I'd like to know how much air is in the tires. The STC thing is the biggest sticky wicket, not something permitted in the FARs I realize. I figure if someone gets an STC for something, me altering it willy-nilly is not quite kosher. Although as far as taking liberties with such things, I guess drilling a hole in a hub cap may be pretty minor. But I just don't know what kind of unintended consequences might result. I don't know what those spinning wheels are doing when they tuck up into the wells. Except getting tangled up in the bird's nest. Perhaps a mechanic can tell me if there is a hazard or a liability risk. I'll have to come to judgement on this. Ultimately I'd like to paint or powder coat the wheels and get rid of the caps, and let form follow function. (The wheels are in really bad cosmetic shape). But of course that means....money.
Incidentally, this site has been great and tremendously helpful since I decided to buy a Mooney, and looked for one to purchase. Now I just have to figure out how to quote and respond!