I have a Countyline 4' tiller made by Behlen (branded Countyline) that I bought at TSC for my BX25. It weighs a ton, but the Kub picks it up without a problem. The website says 595lb and I bought the tiller last spring so I'd guess that's accurate. I also have a Speeco Cat 1 quickhitch so that adds weight (70lbs?).
The tiller is USA made, but has Chinese gearboxes. I'm not sure if the top gearbox can be rearranged in order to make it reverse till. I'd hate to have to take all the tines off and swap direction if I wanted it the other direction.
For forward till vs. reverse till I think I prefer the forward till. If it hits a big rock it goes out the back and it's usually on the top of the soil. I found a 3' piece of rebar in my sister's yard last fall. It caught in the tines, but didn't bend anything on the tiller.
As far as performance I'm glad I didn't buy a bigger tiller. 4' keeps the engine loaded plenty. When I till it's usually with the skids fully raised so it's all the way in as far as it will go.
Attached are some pictures of my setup that a friend took a week ago when I tilled his new yard. The tiller is set on the second hole.