There must be some out-of-round area on that shell. I've never had that issue with any Slingerland or SlingerLeedy bass drum with reinforcement rings. I've owned many. Does your bass drum have re-rings?

No re-rings on this one. It is a puzzle.

I do not have this much trouble with an ovaled Ludwig Supra I have.

Greg, have you measured the drum in more than one spot to check for roundness? I would measure across the drum in a least 4 different points (more would be better - like near the lug points) as shown in the illustration, to help evaluate the roundness of the drum.

In addition to the drum not being round, another possibility is that the depth of the shell is not consistent. Think of a good drum shell being a rectangle when viewed from the side. This could be slightly trapezoidal.

I had an early 80's Rogers snare, just before they went under (go figure) that was like that. Edges were flat, but not parallel to each other. Sounded like Sh#!.

I did measure across the lugs, and it is consistent within 1/8"

Now there's something I did not check! Thanks!!

Shell in round and ruling out defective heads (by trying multiple heads), this may be a bit more challenging to troubleshoot. Hopefully Rob's suggestion may reveal something.

I would also suggest looking at the bass hoop to see if the head contact side of it actually lays flat. I don't think the hoop roundness will be a huge factor like it would be for the shell.

Perhaps a bad head .. ??

If you've tightened it above the tone of the floor tom, it could also be stretched to the point that it just won't tune at this point?

Just throwing it out there, I've not experienced this yet.

+1 with this statement...

Cheers