I have a Merry Mac which is the Northern branded larger 4.5" MacKissick. I ran it on a
B7100 HST which had about 13 pto hp. Your BX had plenty of HP and lift capacity for the larger unit. I would strongly recommend getting as large a
chipper as your tractor can handle unless you're going to burn everything that doesn't fit. Keep in mind that a capacity of X inches means that the material you can actually feed is significantly smaller due to bends, stubs, etc. I got good at angling things just right to get them into the MacKissick but it's better to be able to just put them in.
What are you chipping and shredding?
Do you have a link to that farmers helper model? I don't find it in a search. All I have seen from them is chippers, not
chipper/shredders. If the shredder part is optional I'd recommend the 6"
Woodmaxx with hydraulic feed over either of these. I have the 8" and even ignoring the size difference it's a far better
chipper than the "chuck and duck" manual feed MacKisskic. While it doesn't shred I can get it to chip a lot of the small stuff that I used to have to put in the MacKissick's shredder. It won't shred green material for compost.
There used to be some support for JinMa chippers but they seem to have stopped importing them and the support looks to be drying up. I don't see much at all for FHM but maybe Betstco supports them. MacKissick is American and should be around for a long time.
Get a
chipper with a discharge chute. The MacKissick just dumps below the
chipper so you have to move the tractor every 15-20 minutes or it'll clog.