Hey Mark, hope you're well! I've seen your machining efforts on the forum, and I'm suitably impressed! I need an aluminium/chrome handbrake handle and gearknob for my MX5 as the wood veneer trim is tatty and ick.
If I sent some money your way, would you be interested in making some for me?
The spline was the same diameter, but longer, so it stuck out the other side of the hub slightly. This meant that the drum (and disk) seated on the end of the splines rater than the mounting face of the hub. I drilled a slight relief on the inside of the drum and disk so that they cleared the protuding spline and sat on the mounting face.