Yep, I have adjustable suspension and it is set at its stiffest setting, and raised to the max.
I creeped the "Sheepybuilt" sfwd drag integra and they run a 25" tall tire on the back. So I don't believe I will need a 26" tall tire.
But hey that's why they call it test and tune. I will try em both and see if a 2 inch variance affects the 60 ft or mph on the big end.
In theory, assuming a perfect inflexible circle, a circle will touch a line at exactly 1 point, but since tires are not inflexible, the contact area is flattened a bit. a larger outside diameter will touch a bit more at any given time. This will actually add to rolling resistance.
What really matters for the flexible side is the tire pressure itself. when you reduce the pressure, you flatten the tire out alot more than adding a bit of outside diameter does.
here's an epic paint drawing to help illustrate my point....
So, in theory, the least resistance tire will be the smallest one at the highest pressure.