Thanks Bman, hopefully you can see in this photo how the slide is made. I have a support brace from the barrell to the air tube. It is about 1 1/2 - 2 inches wide. I cut a piece of 16 gauge steel so that it completely covers the air tube opening plus about 3/16 inch overhang all the way around in a teardrop shape. This provides an extension finger on the cover that I drilled a 1/4" clearance hole in and then fastened to the support brace with a 1/4" stud and wing nut. I can loosen the wing nut then move the cover to either open or close off the air tube opening to obtain the desired air flow for the cooking temp I need. I find that it is usually open less than 1/2 inch and will stay at 220 degrees throughout the cooking cycle.
I have problems out of the 'ol back from time to time that limits my bending over to adjust the conventional design UDS. As you can see there are also no ball valves to purchase. The air tube never gets hot and you can adjust the air intake cover with your bare hands. The cover on the exhaust stack stays open during the cooking cycle.
I'll try to get some better photos later this evening.