Re: Pop top cabin support
You don't mention which boat you've got.
Here's how it's done on a Catalina 25: Catalina Direct: Pop Top Mast Lock Assembly
The whole assembly rides up and down in the lower part of the mast slot. The forward lip of the top is held in the U-shaped indentation. The thumbscrew clamps the slider in place.
Joe - s/v Assignment, Catalina 320