SO... I got my new posts and the QD fits just as badly on them. After some noodling, I ended up taking one of the QDs apart and removing the center valve pin. The connector went on just fine. I tried a valve pin from a "regular" black QD and it fits in the Duotight QD OK, but still won't click on, without a lot of force, when put on the post. So, something about the length of the valve pin isn't working with my posts. I 3d printed a mock-up of the valve pin so I could adjust some of the lengths accurately to test the fit. It appears that the length of the second diameter from the back of the pin needs to be .030"-.040" shorter to allow the QD to click onto the post easily. I don't know if there's flash from the production process that is interfering, or if my posts are just made to some other standard than what Kegland used for their QDs, but if I take about 1/32" off the length of that second diameter, things fit well. In the pic, the Duotight pin is the in the middle, and modified "regular" pin on the left. 3d printed pin is obvious.
I didn't want to modify the Duotight pin because I wanted to be able to send everything back if it didn't work out so I focused on modifying a "regular" black QD pin instead which, dimensionally, is quite close to the the Duotight pin (using calipers). So, I used my drill press and a piece of tool steel clamped to the table to cut the diameter back on a "regular" pin. Sketchy as hell, but worked.
The QDs click on easily now, and getting a good pour out of all faucets. Kinda blows my mind that I can have a beer line that is only 15" long and get a nice pour. Really glad these are working out now and hope nobody else has to go through this. If you are, and you come across this post, hope it helps. Cheers.