I have the newer capture plate. For the 3400's Lippert 1116 pinbox, there is just one setscrew. That is in the front of the capture plate. Because it's a $100+ capture plate and because it could quickly and easily "walk away" I use a pinlock to make it more difficult.
When we drop the rig at our dealer's I just remove the capture plate so he can move the Montana with his own truck. It takes me about 20 to 30 seconds to remove it. No adapter needed.
Here you can see the setscrew, the locknut, and the white block the setscrew fits into.
On edit... Pullrite told me the capture plate does not have to be tight. It just have to be tight enough to not fall off. I snug ours up pretty good, though.