I just encountered your second thread on tractor tires. You will get better information maintaining a single thread rather than multiples threads on the same topic. I would have placed the second thread in the KUBOTA OWNING/OPERATING FORUM, rather than the TIRE FORUM.
R1/ag tires have the advantage of casting off manure. R4/industrial tires hold manure in the tread.
If you will operate on public roads, R4/industrial tires vibrate much less than R1/ag tires and have a greater tire area on the road surface contributing friction in an emergency stop.
It is significantly harder to brake a tractor with filled rear tires in an emergency situation on public roads, regardless of tire type. The liquid is spinning, inertia which must be overcome to stop tractor.
Kubota sells tires and has good prices, in my experience. Tires are something Kubota does not price up to to the point owners avoid buying from the dealer.
If you have 4-WD, wheel rims and tires front and back must be proportionally dimensioned for your 4-WD to function properly. If you decide to replace a rim, I would check with a competent Kubota dealer to ensure sizes on tractor now are spec.
THIS THREAD says you have an FEL. No need to fill front tires in that case. Loader is ample front weight. If you have an occasion when the front feels light, which I have never experienced, pick up a load of dirt in the bucket for extra weight.
I lived in Laurel, Maryland for fourteen years. Retired to Florida.