Hi John, don't know how to do exactly what you want re raster3d, but in order to avoid fiddling with the volume viewer I use a couple of aliases which make things faster, perhaps they will be useful to you too:

#Usage cootmode_wire
alias ^cootmode_wire ~rib; disp; color gold; color byhet; repr wire; setattr m lineWidth 2; volume # capfaces false style mesh meshlighting false squaremesh false color "#3333851effff" step 1; sop cap off; set depthCue; set dcStart 0.5; set dcEnd 0.7; background solid black; cofron; symclip 5

#Usage cootmode_wire_white
alias ^cootmode_wire_white ~rib; disp; color gold; color byhet; repr wire; setattr m lineWidth 2; volume # capfaces false style mesh meshlighting false squaremesh false color "#00000000cccc" step 1; sop cap off; set depthCue; set dcStart 0.2; set dcEnd 1; background solid white; cofron; symclip 5

Also, to set maps or diffmaps to given rms level:

# Sets map to x*RMS
# Usage: sig #map_id rms
alias ^map_sig volume $1 sdlevel $2
alias ^diffmap_sig volume $1 rmsLevel -$2 color #da1200000000 rmsLevel $2 color #0000bda00000

Or to just load map and diffmap with model from pdb, and set display settings of maps:
#Load pdb and associated maps from EDS
# Usage: load_pdb_and_maps pdb_id
alias ^load_pdb_and_maps open 1000 $1; open 1001 edsID:$1; open 1002 edsdiffID:$1; cootmode_wire; map_sig #1001 1; diffmap_sig #1002 3

(Requires that the other aliases mentioned already exist, of course)

Cheers,
Oli.