An alternate idea for this end (and it may be stupid) was to run a 2x6 or 2x8 from the A-frame to an adjacent tree.  I don't know how long it would take before the growth of the tree would adversely affect the swingset.  I imagine my daughter using this for no more than 3 years.
 
The drawing shows it coming from the A-frame, but as I'm typing this, I just thought maybe a joist hanger on the end of the 4x6 beam would allow me to do the same thing. Again, these ideas may be a little wacky.
	
		
			
		
		
	
				
			The drawing shows it coming from the A-frame, but as I'm typing this, I just thought maybe a joist hanger on the end of the 4x6 beam would allow me to do the same thing. Again, these ideas may be a little wacky.