That's confusing - you apparently had enough truck for a 14K BP 18' and now are going down in weight to 12K but up in length to 20+5'.
My
M4700 sure fills up my 16+2' Hudson
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But it's a pain to try and park with my 20' truck on a narrow suburban street.
If you don't have "parking" problems I'd say go for it.
I pull the 14k with either my Kenworth which cant take a gooseneck hitch,or Chevy 2500 which Ive never wanted to put a gooseneck hitch on.
After digging a little deeper ... bare tractor is shown by kubota specs to be about 2700#. With FEL (1100#) and a bush hog (1000#) on it + loaded tires about 5200#. Add a box blade 500#, and a disk 800#. that's about 6500 # +/~ ... if trailer weighs 4k, that leaves a 8k payload capacity.
Tractor and implements at 6500 # should be fine for that.
My bumper pull is not a deckover and it limits me to a 5' bush hog. Anything wider wont fit between the fenders. My BB and disk are both 8 ft so they wont go on it at all when mounted to tractor. I have to set them on with the loader, then drive tractor on trailer.
With the gooseneck I could step up to a 6' cutter if I chose too and drive on with the disk or BB on the tractor.
The gooseneck over the bumper pull I have now would allow me to carry more implements with it.
Right now if I go to hunting lease 50 miles away.. I have to go one 100 mile round trip with cutter.. do the work, load all up, drive back drop off cutter and load up and return with disk to finish.
Both trailer setups I guess have their positive and negatives.
If the guy hasnt sold it by this weekend I think im going to get it and give it a try... I really don't have to sell the bumper pull. I can keep them both.