Sheesh, I must have been brain dead yesterday; don't know how I read box blade but thought rear blade.
My Gannon box blade is 42". In my dry clay, it will barely go anywhere. In the hardpan it won't go at all. I have to rip with the subsoiler or rototill first, then use the BB to move the loose soil. It is most useful when regrading the gravel drive. With the turf tires on, the tires frequently just spin when I hit a snag. With the ag tires, it will sometimes snag and stop, but the wheels don't spin.
With a lighter model and better soil conditions, 4' would be o.k. In my thinking, 5' is just too much on a BX. I like the size of this Gannon, but it is heavier than other BBs of similar width. Gannon is now owned by Woods, and I am not sure what the Gannon unit of Woods currently offers in the way of a BB.