A BP&W can indeed be a bit of kludge, particularly if one starts with gear designed for doubles and tries to "adapt" it to singles.
This was exactly what motivated me when I designed the DSS system. Much flatter plate, No STA, *Very* Stable tank, simple to break down post dive, provisions for additional ballast as close to the diver as possible, easier to adjust harness (even without our Glide Harness Adapter)
In short a BP&W optimized from the get go for single tank diving, yet still capable of mounting doubles.
I'd venture 95%+ of the backplate and wings sold in the last ten years will never have a set of doubles mounted to them. Kinda makes sense to avoid adapters etc.
Tobin