PS- I just got my better beamer today in the mail, tried it out inside and it definitely expands the flash area and strength. I look forward to taking it outdoors. It's not expensive and I think it will serve me well. I'm sure that it would serve you well with that 50-500 too since the greatest limits of that lens is available light. Otherwise, it's a dynamo!
Normcar, which flash bracket you use for your setup (if you use one)?