I have the Herd M96...bought it for my former BX-2200 and now use it with my BX-22. No problems.
Yes, you do need to trim the shaft, but that's not unusual in the implement world as every tractor is a little different. When I mount mine, I lay the unit down behind the tractor and deal with the lower arms first. Once that's accomplished I lift it up with one hand, slipping the PTO shaft together in the process. Once it's upright, I fasten the top link and fill up the hopper. Removal is just the reverse. Piece 'O Cake.
This unit was recommended by my tractor dealer as a good solution for the BX and I still consider it a good decision. I would not consider an electric unit on a tractor with a PTO if I had any option in the matter!!!
I find it interesting that the manufacturer is discouraging you from this product. After all, it will work with a type 0 3-pt...which is a really small tractor situation, indeed!