So just to update this thread, I ended up jacking up the rear of the tractor while on a level concrete pad outside my garage. Then I moved the valve stems to 12 o' clock, removed the valve stem cores, and let all the excess fluid rush out. This process took 15 minutes or more. I got the fluid level to the point where there is nothing running out of the valve stem at 12 o' clock, but at 11 or 1 fluid starts to trickle out. To me this indicated that the fluid level is at the top of the wheel, but not above the wheel. Then I reinstalled the valve stem cores and inflated the tires to 15 PSI with the stems still at 12 o' clock. I was able to check the pressure with a pencil gauge with no fluid coming out of the valve stem. I got both sides to 15 PSI and then lowered the tractor back to the ground.
Manual calls for 20 PSI but I like a softer ride and better traction. We'll see how it goes. The tires should be somewhere in the ballpark of 60% full of fluid I'm guessing. I think these 43x16.00R20 tires hold 40 gallons @ 75%. So I'm thinking there should still be at least 30 gallons still remaining in each tire.
While the tractor was jacked up, I was surprised at how easy it was to spin the tires by hand. I expected them to feel very heavy with all that fluid in them. Turns out I couldn't tell there was fluid in them at all. This makes me think that the liquid ballast may not rob horsepower nearly as bad as suitcase weights or wheel weights due to how the physics all works. But that's another thread for another time.....
