[HKS_TRD]

Thats looking great James. I was thinking the countersunk screw idea you originally had would be hard to assemble if not impossible and seems you came to the same conclusion.
What depth does the nut need to be to work for this design? I plan to run a kingpin ballpoint and it looks like this design will be compatible with that.
Another option is to use a bolt inside the knuckle and a nyloc nut on the outside but that may foul on the c hubs.
Another advantage I see in your design is there is no thread in the knuckle to fail, how many f us have had a perfectly good knuckle arm rendered useless due to a stripped kingpin thread.
Will the 3D printed version be suitable for running, I anticipate alloy is best to be able to tighten the screw right up without fear of the nut chewing out the hex opening