Over a year out from his FleaBay nightmare, I finally had a chance to test my friend's "bargain" basement full-face mask, while on a dive in Carmel, after tuning the second stage, just a bit.
Everything worked well in the shallows and at over thirty meters, near a drop-off. No leaks; no wet or hesitant breathing, even while "standing" on my head.
All said and done, he was only within about two hundred and fifty dollars of buying a new set-up, last year -- after the corroded and rat-eaten parts were backordered from Sweden; the labor and kits that I supplied at cost; his continued headaches with a foreigner who had posed as a US seller; and Paypal's odd reticence about getting involved, even in the face of fraud -- essentially, blaming a buyer, for having, unwittingly, dealt with a EU vendor.
Too much effort, for my tastes; but, in the plus column, my friend claimed he hasn't so much as purchased a mouthpiece from eBay since 2019 . . .