Guys,
I just talked to someone who has connections at Kubota and he gave me the skinny on the V4210 cabs.
Apparently, the plastic door skins become brittle when it is really cold and can crack if you slam the doors. Kubota decided not to continue making them and the X model has a different cab style. I think it is still a great deal as the roof, front and rear windshields are worth more than what I paid for the who thing. My RTV lives inside when not working, plus now I know, I'll be careful closing the doors when its really cold.
As I already have seen one door skin crack and know how easy it is to remove, I'm going to line the inside of the door skins with FatMat insulation. I've used this many times on classic cars for sound and heat insulation and it works great. I believe the FatMat will make a energy absorbing gasket between the plastic skin and the metal door frame and will provide strength to the larger unsupported areas of the door. I guess as an added bonus there will be more insulation in the door to keep the heat in.
I find it easier to install Fatmat when it's cold as when warm it sticks like crazy and you only get one chance to put it in place.
I'm not sure if I'll have time this weekend to work on this, but I'll document and post some photos of how it went.
You got tape and other options to fix that door.....still a great deal