Tubes Are not spec'd in circumference. If so, 25" would be a circus clown balloonthat is for an circumference going from 24 to 25.
For diameter you would get....about 8% ha ha.
so a 1500lb capacity goes to 1620 lbs. Not that much unless you are right on the edge of capacity.
That's a 46% increase in cross sectional areaWhich Sotar design? I went from a 19" to 23"x 14' Sotar ST this year- Big difference, but maybe not quite as much as I originally thought it would be. I wouldn't think you'd notice a difference between the two-
That's what I was telling you about weight ratings. Maravia gives "max optimal" weight ratings, allowing for 1/3 of the tube to be submersed. If you take 15-20% of that weight off it'll perform like Papushka the dancing bear!