The NH tractor seems a little small for a mid blade.
Several people have built a land plane for the 3 point hitch,,
I built one, but, for  a slightly larger tractor.
	
	
	
		
		
		
			
		
		
	
	
	
	
	
		
		
		
		
	
	
I used the cutting edge off of a CAT 14 foot motor grader,, (two 7' blades)
It does a remarkable job.
	
	
	
		
		
		
		
	
	
I have considered building a smaller one also.