Dometic Update:

Problem found... solved?

I gave the burner jet a very thorough cleaning: hydrochloric acid /
sulfuric acid flush (from some hot-tub chemicals I had laying around)
followed by a 99% isopropanol flush.  It seems to have made a big
difference in flame height.

Updated pix here:
   http://xochi.com/vanagon/dometic/

Notice particularly the side-view before & after shots -- i'd estimate
that after cleaning, the flame size/volume/heat output is now at least
double, if not triple what it was.

Now to reassemble & test in the van (for the 4th time!)