I would say that 16' is too short for your needs. 18" would be marginal and 20' would be about perfect.
With the BH on the tractor and the box blade up front by the rail (best place) and the FEL against the Box blade you will have your weight about perfectly balanced. The shorter trailers would get you tail heavy (the 16' probably dangerously so).
The tilt bed one shown would be very nice too. But spendy. I like slide in rails for tractors. They allow you to go extra long on attachments. The flip up ones would give problems.
With the BH on the tractor and the box blade up front by the rail (best place) and the FEL against the Box blade you will have your weight about perfectly balanced. The shorter trailers would get you tail heavy (the 16' probably dangerously so).
The tilt bed one shown would be very nice too. But spendy. I like slide in rails for tractors. They allow you to go extra long on attachments. The flip up ones would give problems.