For another couple of hours, I own (3) First Run Buzzz OSs. The two I have with sunken tops, which were impossible to flatten are getting sold to a guy @ league. They were not high speed overstable, and would not hold a hyzer line in the high speed portion of their flight, but they never flipped all the way over, either. They have plenty of LSS and finish left reliably. The third one is a very nice green color with a "normal' top. Some shoulder with moderate dome. It is almost unthrowably overstable. I am able to throw Zones around 300', and I am not sure this disc is any longer, if as long. It may make a fine forehand disc, but I probably won't find out, as it is likely headed to a new home as well. Meanwhile, I am looking at replacing my GLO FLX Wasps with Z Nebulas. I like the speed and dependability of the Nebula mold. I wasn't sold on it at the ACE Race a couple years ago, but the Z Plastic improves it, IMO.
So, check the dome on the BOS you are thinking of buying. I would like to try one that had a truly flat top, assuming (I know), that it would fall between the two versions I have thrown.
Food for thought.
KP