Nice work, Michigan!  I have a similar sized 'bator and it has ~8 holes on the back side.  Some toward the bottom for cool air to flow in, some near the top for heat to flow out.  
I would want at least one upper hole to encourage ventilation, right now yours traps the hot air at the top (unless you have a fan blowing it back down somehow, the hot air will stay up there).
		
		
	
	
		
	
I have a turner now, but this shows the inside.
		
	
	
		
			
		
		
	
				
			I would want at least one upper hole to encourage ventilation, right now yours traps the hot air at the top (unless you have a fan blowing it back down somehow, the hot air will stay up there).
	I have a turner now, but this shows the inside.
	
	
	
	
	
	