I like the door opener concept as it allows very small adj. during the dynamic movement....like a turnbuckle type adjuster....I may make one out of heavier gauge fine-threaded rod and large fine thread spacer nuts...also more force and finer adjustment available with the screw mechanisim.....I see the square area on the IP you are talking about.....this is good info...maybe combine these two clever designs....A nice rig could even be left in place like the adjusters on the belt driven stuff....keep on thinking guys!....kevin