Yes, I think the original files had a problem with the launcher (TNV_54321) files being transferred over CMA. But since then the files have been updated, theres even a pack on the
TN-V download page for 3.50 WoP.
I'm not entirely sure its working, since I have 3.36 and just made the custom bubble right away. But try making sure the TNV_54321 makes it to the Vita, I actually realized it was not transferring and used FTP to move the launcher over before the fixed files were released. So if they still wont transfer you can try that!
EDIT: Welp, I saw that post you were talking about, that its not %100 working, so maybe the best option is..
There is a third option...
[spoiler]Since you're on 3.50 you can access PSN and download Ape Escape and use the available exploit to load TN-V, plus its way easier and you dont need a second device![/spoiler]