Technical Is there a trick to getting these repro 41 caps to stay on the damn wheel?

Just doing a little searching brought this up.
Looks to me that your problem may be just that, you’re trying to use a reproduction cap designed for an aftermarket wheel.

https://www.speedwaymotors.com/1941-Ford-Hubcap-P***enger-Car-Stainless-Steel,3095.html

Here’s some of the description text from the ad:

Info
These reproduction hub caps for stock 1941 Ford wheels are constructed of polished stainless steel. They feature the cl***ic "Ford" script in center and attach using 4 original Ford style mounting clips (not included). Measures 8-3/16" at its mounting flange and 9-7/8" at its face.

• Perfect detail
• Stainless steel
• For 1941 Ford wheels
• Attach using 4 original Ford style mounting clips (not included)
• Measures 8-3/16" at mounting flange

 

I'm using OEM wheels and reproduction caps, made for OEM wheels.

The repro caps are two piece, lighter gauge metal, and not deep enough to grab securely.

OEM on the left, REPRO on the right

 

It's bent, this piece is supposed to be 90 degrees.

 

The REAL solution...

Separate the new two-piece cap by prying back the metal holding the two pieces together.
Cut the back from an original cap, making it the exact size of the old piece. Insert into
the new cap and gently pound the ridge back to hold the old back in the new cap.

It aint going nowhere now.

 

We knew you could figure it out.
Good solution, isn’t that what hot rodders do,
modify things to blend the old with the new and make things work?