Mr. Guffey,
I believe you have come to the correct conclusion!
Higgite,
Take a look at Sinclair's bullet comparator inserts. They'll fit your Hornady adapter. They are stainless steel and the hole is cut with something closer to a chamber reamer than the aluminum Hornady parts have. As a result, the Sinclair inserts contact the bullet a little further down, but it's nearer to where actual contact will occur anyway. They also make their own insert adapter. The only difference between it and the Hornady is that the Sinclair is centered and not offset to work with the Hornady Overall Length gauge, as Hornady's is.
I had a drawing of the gauge I gave to somebody, but I'll be darned if I can lay hands on it at the moment. I'll post it if I come across it.