Welded up the axle from 40mm box with a 3mm wall. Cut them at 16 degrees to match the king pin inclination on the yokes from Gemini. I also added a 5 degree caster angle. As I have mentioned in the thread "top hats", I have struggled to assemble the two tubes and top hats, so much so that even clamping them in the vice or with a G clamp it was difficult. In fact I broke one of them but I have used a piece of HDPE in place of the bit that broke off. Larger diameter outer tube would be better with a bearing or oilite bushes. When I changed the stub axle bearings I couldn't find any crush tube with a 17mm bore, so I cut the 15mm ones along their length and increased the gap and consequently the diameter that way. The springs seem to be working OK so far. I have attached some pictures, but I will add some detail pictures tomorrow.