Not a thorough test but today I used a naked (no rf shield) 580exii with my PW flex unit. I got a reliable trigger at 52 feet using another TT5 on my 5dmk2 in ETTL mode.
Same exact scenario but I swapped out the flash to a 600EX-RT. I gained 8feet. So in otherwords I got 60feet reliable trigger with a 600EX-RT with no shielding.
I should have taken more time to do more testing but ran out of time today.
Hopefully I'll get more 600ex-rt's to complete a different system that allows me to get more reliable range.