Fussell's book is a very entertaining read, he is a superb observer.
Beware: whatever you do - or don't, whatever you wear - or won't, you cannot not send out a class signal. Reminded me of the passage in one of Konrad Lorenz's books where he goes out to a lecture dressed in suit and tie - all his students wear jeans and shirttails, the males have beards - until he realizes it's just his own "uniform", a predictable and laughable way of asserting his status.
Fussell points out that proles can't write the "'s" correctly, more and more writing Dennys instead of Denny's. Here in Germany, it's the other way around: our proles write Wilhelm's instead of the correct German Wilhelms. They go to Pizza Hoot (Hut - pronounced "hoot" is German for hat) - the new logo even suggesting they were right in the first place.
To me, your class is not what you were born into but what you unthinkingly kept from that. Fussell is right - it's not money but culture. However, like all cultural topics, "high" and "low" change from place to place. The principles he points out are valid for everybody, the details just work in ivy-league-educated, WASP-dominated New England.
The X-concept works - if approached on the basis that you make your own decisions. If you just emulate Fussell's examples, your non-legible clothes become legible as well.
All in all, a fine argument for class before mass - not that it'll stop the relentless onslaught of the low-brow, but for a few more years there might be niches for civilized living (as opposed to hum-drum existence or mere survival) if enough people read it and act accordingly. The market offers what consumers want - the choice is up to you and me.