There were three limitations to making them spot-on

1. The original cap has the convex center that raises above the level of the wheel surface; the prototype caps dish following the curve of the wheel.
2. The room behind center cap is very limited by the dust cap over the axle end. That makes it difficult to recess the socket head bolt
3. I could not find bigger socket head cap bolts; the ones I used are quite large (though appear small in photos) but not large enough to match the proportions of the prototype.

To really capture the look, a full repro cap would have to be made...

I imagine a nice billet piece turned on a lathe would be just the trick. (Ouch$)

I have a spare set of original caps so I can switch. Today I will take it for a spin and have another driver tell me if the bolts are centered. If they're really bad I will probably be able to feel it in the balance...