FYI
How I did mine
carbon rudder shaft
made template of shaft and what I wanted outside shape
I got a block of ally from Ullrich and gave the lot to really good machinist in kumeu total cost with anodising for arm $650
Cut the tube cast the arm onto shaft, built shelf bit more work and all good....the ram was mounted above deck connected to tiller years ago by someone but that in my mind is just wrong for a ram not designed for it.
We also did a test piece of the shaft and cannot remember exactly how much to break it but it was definitely above 2.5 tons for my piece of mind.
t