You're going to need a fairly thick mounting bar so that you can get a few full screw threads in it to support the pickup without it being wobbly.
Yeah mate, I'm thinking a minimum 3-5 mm thick and probably thicker in the middle. I need to review the neck angle to set up the angle of the mount and the screw holes. It's all a bit theoretical at the moment.
FrankenLab Hand crafting guitars, because Death Rays are expensive.