modeling challenge

I've got a modeling problem. I'm trying to accurately create
this... but so far all I've managed to do is waste a bunch of time.

(note the bottom image is a radiance image)

Currently I have two individual cylinders each as a rad file.
Then I have a scene file that xforms these into a ~16,000
unit array. That file is then rotated and transformed onto
the building by an additional scene file, which is then
called by oconv by a "rad" like script.

It works, but it takes a very long time to oconv (I guess b/c
it has to run xform 16000 times and Radiance on Cygwin is
very slow at this based on benchmark results) and so far I
have been unable to create an actual rendering for some reason.

What is your aim? Are you trying to create an accurate internal lighting analysis, or generate a nice render from the outside? If
the latter, there are all sorts of ways you could cheat - starting with texture / bump / alpha mapping.

Have you tried modeling this without using xform? ie: use some sort of script to generate all the cylinder geometry in their final
positions so that oconv has less work to do?