Need help with sun simulator design

[GaryGary]

Hi,
I've been working on an indoor sun simulator so that I can do solar thermal collector testing indoors and without always having to having to do side by side tests with a baseline collector.

The sun simulator currently uses six 400 watt metal halide lamps to light up a collector that can be up to about 2 by 4 ft.

Its coming along pretty well, but I'm having some trouble getting to a reflector design that gets enough of the lamp light onto the collector. If you have a minute to look at the setup and make suggestions, I'd appreciate it.
All the details here:
A Sun Simulator for Solar Thermal Collector Testing

Its on the long side, but you can skip down to near the bottom and see the
problem.

Gary