Do you see any strength issue, comparing that base-plus-valve scheme with the one-piece bronze casting that incorporates a ball valve? (I am not questioning the worth of the design, just looking for some informed opinion...)
Thanks,
LB
Have measured it against many other seacocks including Spartan and some old WC tapered cones and it is a very robust option. Nominal wall thickness on a 3/4" flange is just shy of 5mm thick at the base and at the NPT threads it is just shy of 3mm thick. The nominal wall thickness of an Apollo bronze 3/4" thru hull is 1.5mm or about as thick as a US penny.
So the 3/4" flanged adapter is about twice the thickness of a 3/4" thu-hull which builders like Hunter still slap valves onto, and we rarely hear of a failure. Ericson did the same thing only in Marelon. At double the thickness of a thru-hull wall I doubt you'd ever see one fail.
EDIT: For grins I just measured a very old and "robust" 1 1/2", not 3/4", tapered cone seacock I have in the barn. The nominal wall thickness was about 3mm.
They far exceed the ABYC strength requirement as do most bronze seacocks but the benefit of easily replacing the valve with a brand new one without affecting the integrity of the thru-hull and flange is a huge benefit....
If I was going to have permanently installed bronze seacocks they'd be Spartan's. Of course those run $300.00 +/- each and require yearly maintenance. Much easier to spin a new valve on every ten + years or so...