Quote - Instead of using the USGS ASCII DEM directly in VUE,  I opened it in GeoControl2.2.....

....wrong!  Sorry....I did it as you did, i.e. used 3DEM to convert the MOLA selection to a .ter, 
then opened it in GC2.2, and converted it to all the available file types.

So far have only tried the 512 .obj mesh......very dense. I couldn't see how to decimate it in VUE, only for preview renders.

But will try the others, e.g. tif , bmp, pgm (for Bryce), etc and see what gives the best results.