Also just found this,
Open mame, select "vertical" filter on the left, click at the "floppy
disk" at the top of the screen and select the first option to create a
XML file named
inside the
ui folder. Open
Clrmamepro, click
Add DatFile and select the
file, click "OK" to whatever shows up.
No need to change any settings, go to
Rebuilder, at
Source select your mame roms folder, at
Destination select where you want to create your vertical roms at, click
Rebuild and wait.