Not sure how to answer the poll regarding my ST Pro.
At some point Stern switched backbox designs to use the larger hold down bolts that match the legs. I got a main cabinet designed for new larger bolts and those bolts were in the bag but the backbox was actually designed for the older small bolts so I couldn't fasten the head down as recommended (so "playable" in this case is subjective).
I went to the hardware store and got some shouldered bolts that worked great and Stern sent "factory" bolts a few days later ( I kept using mine because they fit tighter) Other than that it was fine.