(I still only got 10 gallons drained out with all 4 plugs removed.)
I just completed my 50 hour service and I also only got about 10 gallons out with all 4 drain plugs removed, I guess Kubota's figures are base upon a dry unit because there is probably more SUDT still in the system that is unable to drain.
The drain pan I ordered was delivered and IMO was worth every penny. I didn't spill any substantial amount of fluid on the floor, although there was a few little splash drops from when the fluid first hit the pan.
The pan has a three inch drain hole with four smaller holes down inside, I assume to prevent dropping the tractor's drain plug(s) down into the pan. The pan comes with a screw in plug for the drain hole and four places to prop up filters to drain, there is a small removable screw-in plug in the corner to act as a vent, and on the end there is a drain spout with a screw on cap to empty the pan. Furthermore, the pan has a plastic wheel shaft on one end to help move the pan around while you are on the ground. Once I installed the SUDT into the tractor, disposal of the old fluid was fairly easy. I set the drain pan up on top of four 5 gallon buckets, with some wood blocks to elevate the pan, and drained the old SUDT back into the new SUDT buckets. I highly recommend the pan as it makes this job a lot less tedious.
Jim