Sorry to say this, but if I read the dimensions correctly on the stone (4" deep, 8" high?), they're nat inteded for a free-standing wall, & subsequently wont last long , regardless of dead-men, versa-grid, all stone backfill, etc. It sounds like what you are using is a stone veneer, meant to be applied where there is block or wood framing back-up to tie it into. The stone used for free-standing work should be in the 8"-12" deep range, & 4"-6" height range. I hate to tell you, but I think the stone your using are too "tippy" for this application. Hopefully you mis-typed when you listed the dimensions.