Marc,
If your fill tube is solid and not leaking at the pan, I would advise just sticking a dowel rod down the fill tube to the oil pan bottom (tractor needs to be level). Measure the oil on the dowel rod. Add oil as needed until the dowel rod shows 2-3/8" of oil in the pan. Now recalibrate the dipstick with a file marking (easier than shortening the dipstick). In doing this, be sure the engine has been run after the oil change so the oil filter, oil ports, etc. are filled. Draining the oil pan with the front left of the tractor parked downhill will still leave some oil in the pan.
Harold