Rear tires are 43x16-20 and supposedly will hold about 38 gallons each. Used 3 gallons each of -50 antifreeze. I guess that ought to keep it no worse than slushy down to 27F-ish. That's enough for the Dallas area and garage storage.
Total cost was $57 installed (tractor was already at dealer for other work). Should weigh about 315 lbs per tire. 630 lbs for both tires. That's 9.04 cents per pound. Using more antifreeze would of course up the cost.
If we use rimguard at $2.37 per gallon installed as mentioned above, that's $180 for the same fill. Would be about 410 lbs per tire or 820 lbs total. That's an extra 190 pounds, but it's also 21.9 cents per pound.
I chose the 630 pounds for $57.
In a colder climate requiring more severe freeze protection, Rimguard might quickly become cheaper than adding lots more antifreeze.