Back in the late '80 and early '90s I had my own hair very long. At it's longest it touched my elbows, which just shy of waist length. I'm very slender, too, I think I was usually taken for a woman when seen from behind (and often from the front, for that matter). A few times I even had men open doors for me, doubtless assuming I was a women. I, of course, appreciated it.
Toward the mid '90s I cut my hair fairly short again. One of my first online purchases was a waist length blonde synthetic wig. It never looked very believable, though. For one thing, most blonde synthetics look plasticy. The main problem with making a wig look convincing, though, is the hairline and to a lessor extent the head shape. Unless the wig is a lace front with the thin mesh you adhere to your forehead, the front of the wig is pretty much a wig giveaway. Also, you might notice that with very long hair the hair lies very close to the scalp around the head. You rarely see a wig the fits to your scalp that closely. If you had a full lace wig custom fitted to your head, then shave your head it might come close to that look. I've actually seen some bald alopecia ladies who manage to achieve that look pretty well, but you won't get it with most wigs and with hair under it.
