Do yourself a favor...go buy a SS BP - be it Koplin, Halcyon, etc. and buy a 2" webbing kit with SS D-rings, SS buckle, and SS sliders. For about $180 you have a complete 'harness' - no gimmicks - no Fastex buckles, etc.
I have an OMS IQ and SS BP, and its fine - but you really don't need a $200 harness and $100 BP to make a BP and harness.
For about hundreds of dollars less you can have an entirely serviceable kit and $20 worthy of webbing will last for years - and when it doesn't - you simply buy $20 more of webbing and restring it.
Deep Outdoors or OMS harnesses are nice but the Fastex buckles add a 'potential' failure point or may get cracked if you step on them or drop a tank on them by accident.
Why spend $300-600 for a harness when you can spend about $180?