This is by no means a complete or scientific test, because I simply have not had them out enough to give firm results, BUT:
I built 16.5 beadlocks (actually BillaVista did for me) using 'standard' 8.25 inch wide rims (4.75 bspace) and rock stomper bead locks. Ended up 9.75 wide, 4.75 bs, 16.5 beadlocks.
I have used them for 3 rock crawling trail runs, running 38.5 14.5 SXs aired down to 5 ~ 6 psi.
So far I have NOT lost an inner bead.
If I start losing inner beads then I will do the inside safety bead thing.
They are super easy to mount the tires on, much easier than 15 inch rims.
They WILL lose the inner bead a lot easier. For instance, when the tire goes flat, with weight on it you lose the inner bead.
BUT so far with 5 ~ 6 psi in it I have retained the inner bead.
Not that hummer rims aren't cool!!!!