I've been out of the game for a good while, and haven't really kept current. I have had a few Yugos, and a couple with the SB47.  Ut recently I picked up another yugo that I had planned to SBR, but decided against it. I picked up a Shockwave and have decided to go that route, but am curious as to how it has to mount. I have a stormwerks hinge and a ST tube adaptor, but am not sure if threaded the received for the hinge and adaptor will create a "rifle" or not. My suspicions are yes. If so, then I will order the US machine gun hinge/rube mount that mounts under the grip the same as the SB47

There has been no ruling prohibiting any particular method for mounting a brace to any handgun.

- OS

What are some recommended pistol brace attachment tube sets/ parts?

I have the Sig Galil style brace from Atlantic Firearms on my Draco.

No issues.

It is worth noting that ATF did of course issue a letter (since someone demanded specificity so many times they had no choice) that technically shooting with a brace from the shoulder could be construed as an illegal SBR; however, provided you aren't seen by anyone doing so (as in you always use the brace as intended when in public/around strangers) then you won't run afoul of the law.

Simple possession and use of a brace doesn't constitute an SBR though.  Just mis-using it, according to the ATF letter of a couple years ago.