yesh that's right~
I asked because that mask looks like an awful lot of wasted texture space... if it can be RLE'd then at least you aren't wasting too much bandwidth in release, sending it back and forth over the net. I don't know enough about video cards, and if they can handle that type of compression either, but if it were me I would probably have UV'd the alpha stuff onto a separate map so the mask could be small as well, and get some more texel density into the remaining majority of it. Though maybe that's a bad idea for other reasons ..enlightening thoughs, anyone?