I found this interesting. I hope you will too 
Over the past week or two I've been re-working an indirect adapter I originally put together perhaps two years ago. It allows a reverse-mounted studio flash to be repositioned inside a suitable modifier by sliding a central 5/8" shaft either in or out.
Though designed for use with studio storbes, since I had the required components on hand, I decided to test the adapter using a 71" Rimelite Grand Box along with a CL-360.
The amazingly useful Manfrotto Camera Platform was once again pressed into service. It allowed the CL-360 to be mounted parallel to the central 5/8" rod while also allowing the flash to be easily slid forward or back along its length.
Overall, this is what the assembly looked like with the CL-360 at 1/32 power:
Here you can see the flash at near, middle, and far distances (the clamp on the end of the rod is there to prevent me from carelessly sliding the 360 off into space):
The first thing I found interesting was that the Rimelite Grand Box does seem to be almost parabolic (in the mathematical sense) as meter readings jumped by a full stop when the flash was moved to what is apparently the focus of the modifier. The best meter reading was produced when the base of the flashtube was 13" from the apex of the modifier.
The second thing that surprised me was how much light was coming out of the 71" modifier when using just a single CL-360. At 8' from the front edge of the Rimelite and the meter at ISO 200 with the CL-360 at full power:
Base of the flashtube at 10": f/32
Base of the flashtube at 13": f/45
Base of the flashtube at 16": f/32.2
Base of the flashtube at 23": f/16.9
This, of course, tells us nothing about how the light falling on a subject varies as the flash is moved in or out of the modifier. However, it does provide convincing evidence that the 360 (whether CL or AD or other) has no trouble at all filling a large parabolic modifier with adequate amounts of illumination for most situations.
For those of us who aren't Leo, a Rimelite Grand Box with an indirect mounted strobe (or strobe head) is probably as close to a Bron Para as we're ever going to get.