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I recently got the new base and I can confirm there is a bit more adjustment than the old one pictured above. If I was to guess I would say you can get about 3-4 additional inches of adjustment with the new base.
On my 3 year old B & W the uprights have 8 holes instead of 4 as shown in your picture. Also you can swap sides with the uprights & move the center of gravity fore/aft maybe an inch.
Travelin' Texans
Former '13 FB owner
Currently rvless!!
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It appears from your top down photo of the base that you uprights are in the rear position. They could be moved toward the cab which moves the hitch point forward as well. I can't remember for certain, but the uprights may end up swapping sides to make this happen. The older style base is the Model 3000 (I have one). I have attached a manual for the 3000. Look at Figure A.
I hope this is helpful.
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