No, not the case at all. See attached photos. The B2920 photo (having the loader up high in the photo) has a part of the frame that is about 4 or 5" high, a foot or so wide, and flat facing forward. The B2150 photo shows a very similar part of the frame, also flat and also facing forward, with various bolt holes, etc. I have 2 of the B2150s and have a set of Kubota suitcase weights that simply hook onto that flat forward facing part of the frame. Each one is 55 lbs and I have 3 that fit on at the same time.
I can't see any reason why your B2920 would not accept the same suitcase weights as-is with no adapters or brackets. If you have trouble finding Kubota weights take a look at
Suitcase Weights - Lonestar Weights Also I see quite afew being offered on E-Bay. There are no doubt many sources and you probably don't care if they are orange ...Essentially all of them are designed to just "hook over" a flat front facing steel plate, in your case part of the frame of the tractor. You could probably bolt on a 1/2 inch thick steel plate (that would be a lot wider than your existing frame member) and put on several more weights if you felt you needed them.