Thanks! I got her from down South (Carver) and she's bright orange, so the name fit.
I have aggies on her. My neighbor had R4s, but because of the steepness combined with that classic New England grayish-brown clay, he got stuck so often he also switched to ags.
The sad fact is the L3010 has a fairly wimpy power to weight ratio (both the B2910 and the L3410 are better on hills). The only time Clementine has ever seen high range is the time we drove into the village to have her bucket hooks welded on. Probably 75% of the time she's in low, though I typically get away with mowing in mid range by traversing the slope from top to bottom. My meadow has a 22% grade: pretty steep when hauling anything.
Can't really answer your question about the difference in climbing between loaded and naked tires. They were unloaded only in winter when the tractor was stuck in low range and wearing those Norse ice chains.
Not sure how many gallons are required; any tire shop would be able to tell you, though.
Have fun. It's a great rig!
Pete