I pull a 6' KK box blade behind my BX2230. I bought it on EBay and it was advertised as a 5', but when I got there to pick it up, it was 6'. It works well for my needs. Mostly smoothing surfaces with front blade digging very little or only clipping the high spots. It's too big for any real digging, but I can pull it up to about 3/4 full. Above that and the blade has to fill the trenches the tractor is digging just trying to pull it.
If anyone wants to trade a 4' of 5' BB for my 6' KK, PM me! I'm in NW Connecticut.