Like i said, UltraARC just have Pcomp046 inside, nothing more (somehow it uses cls + exe for compression without any arc settings).
Try to use like this
MMC=PRMT+srep+lzma2
and check MMC in GUI.
As for MSC: You could find it in 0 + 1 + 2 txt. Just make sure you don't use DDS compression (it's buggy as hell in 0.0.6.4)
Edit:
You could also try with ArcGUI instead
http://fileforums.com/showthread.php?t=98152
I think it's a nice UltraARC replacement (it's with masked compression too!!
)