Follow up notes on One Ocean:
I recommended to my buddy who wanted an adaptable mast he buy the One Ocean and he's been riding it for months now and used it on multiple brands. I asked him if there has been any weird issues with it, any problems, ventilation, anything at all? He reports no concerns other than drawing too much attention on the beach as the stiffest mast around.

I have also been privileged enough to ride it. I went straight to trying to make it fail myself and was unsuccessful in every way.
It's stiffness is clearly competition for the top of the market. I'd easily place it in the top 3 masts I've ever ridden and at that point I can't tell the difference from one to the next. The pump and glide is outstanding, easily the best I've experienced at that size. It's beautifully made, every little detail on it is masterfully executed.
A note on the adapters:
A shop that is selling a different adaptable mast made some negative comments in a youtube video about the adapters being chunky and draggy when they come from Stringfellow. I'm not sure if that's where the negativity started but it seemed to catch on a bit and I've been asked questions surrounding these adapters since then. I have not tested them all but what I can say is this: I rode the Stringfellow AFS adapter on the One Ocean 78SSS mast (12.2mm thickness 102mm chord) back to back vs the AFS 80cm UHM (13.8mm thickness 115mm chord) mast which is the AFS gold standard. Same parawing, same wind, same section of water, same front foil and tail. The One Ocean was faster on all recorded upwind and downwind data sets. So, I think you need to look at the mast as a whole and how progressive this design is and how high quality the build is to make a decision on if it's right for you.