Darren,

It doesn't look right to me.

Below see the same cap on '54 wheel. Notice the face of the cap DOES NOT break this wheel's outer plane. Also, the edge of the cap is held snug against the wheel.

Is your cap held on nice and tight by the retainers? Maybe the retainers are too long for this style cap.

I'm no expert but think Hudson offered several versions of caps during the StepDown period. For instance I have another set of caps that are slightly smaller diameter and do not fit the wheel shown in the picture below. They are what I term a smaller dog-dish style cap. See pics below.   

These caps were on the car when I got it. They seemed to come off pretty easily. Here is a pic while it was parked in that barn.

Excuse the duplicates. I'm still learning which buttons to press.

I wonder if there were different caps if the car was ordered with trim rings?
I also noted that of the five wheels, one had a kind of oval shaped valve hole. By the serial number, the car was a later build. Could that have been something transitional?

Looks like you have 15 inch hubcaps on 16 inch wheels. you also need trim rings to go with them

Those are 15in. wheels. Any idea where I could score the correct caps and rings?

Darren ---Remove a cap and take a picture of the retainers. Also measure the length of the retainers and the distance between them (post this info). I'll gather the same information from my wheels/caps. I'm now second guessing my prior comment (not looking right) and maybe the caps you have are NOT the problem---the retainers might be bent or too long.... 

Deleted. Try again.

Good grief, I thought I was better at this than I am. Here goes again:

Darren ---Have a look below. If yours are wrong so are mine! They say misery loves company...I honestly thought the back of my cap sat right up against the wheel ---wrong, it actually sits approx 1/4" away. Bottomline ---I now opine your caps and wheels are fine. 

Haha. Okay, then. Now I jist need to know what to measure to get the right size of trim rings...and where to get them from.

For trim rings, just ask for 15" trim rings. They will give you the right pieces. C.W. Moss, Speedway Motors, Arrowhead Truck Parts, Bob Drake, Mac's, all sell them.

FYI, the same hubcaps on my 1953 Hornet also sit a little off the wheel disc.  Not much, but enough to allow me to get my fingertips under them to pull them off.