I had a '96 Tantrum and a friend had a '89 251. I didn't think the 251 had a pad. The 251 was very reactive to anyone moving around in the boat. He was constantly adjusting the tabs to keep it level at slower speeds. I believe the 251 was a little narrower than the AT. The AT was very stable compared to the 251, but I thought the 251 cut the water better(LOTO).

So...... what's the question?

Lots of things cause a boat to list at different speeds...
What prop? pitch? style? direction?
How is the boat trimmed at the speed you're asking about?
What side is the battery on?
What is normal cruise load?
All of these have some degree of effect,

I have a super clean 98 with 500hp procharged FS

I noticed listing occasionally at lower speeds. With the right trim and tab it evens out. I wonder if I could change props to get a bit more mid level performance.

A single engine boat will almost always list at some speed(s); especially when it's a true V-bottom and no pronounced pad.