Well I used two lengths of SST tube. I machined up a teflon sleeve for the larger tube so the smaller could snugly and smoothly slide inside. At the other end of the smaller tube, I machined another teflon sleeve to act as a spacer so as the tubes slid in/out smoothly without binding. The ends I machined from Aluminium and anodised them myself. However a good etch prime and paint
would do fine. In side the two tubes is a large Galv spring. That was the hard part to find. I wanted to find a SST spring, but couldn't find one the size I wanted. So Galv it was. It is not 3yrs or more and I just had an issue the other day with the vang binding. Turns out the inner tube I used was not SST. It was piece of tube from a chines something and was only plated. So I have the unit off the boat and am going to replace the inner tube with SST. The end fittings had sheeves in them for the line to run around.
I have it out in my shed. I will take a photo
of it and post it. But I can't do it right now cause my camera
card has packed a sad and won't work. I have to go buy another memory card.
As for l;oads on the Gooseneck etc, that is not actually a problem. Firstly the vang line takes the boom loading. The rigid Vang is there for no other purpose than to support the boom when the sail is down. There is no compression
load seen on the goosneck other than the weight of the boom itself when the sail is down, which results in a pull not a compress. My boom is 8M in length. I have the Vang fitted at 30dg. The 30dg was to get the support down the boom more. The main issue is the boom bouncing. The further down the boom, the more support and less bounce.