I have 2 50 round 762x39 50 round waffle mags made by yours truly. Yes it is legal.
$50 each shipped or $95 each for the pair. Will also trade each for 2-223 waffle mags or a 762 40 round waffle and $15.00. I don't have the hang of posting pics here yet so if interested you can look here:
or email me and I will send you a pic.