Hi-
The volume rendering options and all those parts are for the TT_N27 file-- that was the one you wanted to make a 'volume', and not just slices. So, you still need to load it in, using:
suma -vol TT_N27+tlrc. -i_ply OUT_PREFIX.ply
Then you can follow the volume rendering steps from before using the object controller panel for TT_N27+tlrc.
I had meant that if you wanted to, you could try:
suma -vol TT_N27+tlrc. -spec N27_both_tlrc.spec -i_ply OUT_PREFIX.ply
Again, I don't know how this *.spec file was created, so I don't know if it's causing a problem or not (I don't believe you need it here anyways, since you just have one *.ply file).
--pt