Kmw1954,
Alright, I am now unconfused. I forgot that new Lee design was progressive (or semi-progressive if that is more apt; I'll have to watch through some videos on it and download the manual to see which it appears to be).
Regarding the Dillon (other copies may show up), keep in mind its lifetime warranty travels with it from owner to owner. It's part of what you pay for. There is, indeed, a retrofit kit with a new frame and automatic primer feed and case-operated powder measure. I got one for my dad's 450 for Christmas one year long ago. If you can swing it at some future time, you will have a press that can reload most common cartridges and that may be switched over in a reasonable length of time.
One thing you said puzzles me, and that is that the .451 and .452 bullets didn't seem to feed any better or less well than one another. I assume that you meant this was so before the Lee CFCD was brought into play. If I am catching that correctly, then I don't know what's happening. I was expecting the CFCD might be taking some of them down a thousandth, but if a thousandth doesn't matter without the CFCD, it seems as if the diameter limiting function might not necessarily be responsible for it fixing the problem. I'm wondering if maybe your picky gun likes the slope of the Lee taper crimp better. Have you compared the shape of the taper crimp in your standard die set to what you get out of the CFCD? Have you measured the OD's over the bullet of both your bullet sizes before and after they come out of the CFCD?