About 3 years ago I was asking for help on what it meant for setting & checking the stack height on a convertible top. The manual was a bit elusive & with many years of thinking about this I finally think I have it figured out. The "Stack" height is the combined height of the convertible top frame when it is in the collapsed position ready for the cover. It should be as low as possible so it doesn't stress the cover any more than it has to when down. This is usually set for life at the factory & only needed when the frame has been off the car or there are major alignment issues that the top adjusted can't take up. Once this is set you are ready to adjust the rest of the frame to fit the car. Here is a snippet from the FSM Keep in mind that dropping this after a top is installed will likely affect the fit of the top so I believe it's important to do this when replacing the top only & making small adjustments to the top frame only when needed.