Having just bought a tonneau, the design unfortunately doesn't work with my harnesses (they'd have to pass through the tonneau when it's on the car, and they aren't the unclipping type).

Is there any kind of carabiner type device I can safely use to make them unclippable or do I basically need to buy a new set of harnesses?

Could you move the mounting points to the roll bar? Might need a bit of welding but might solve the problem. See in my archive for picture.

Yeah, that's where they currently are - the problem isn't the boot cover, but the passenger / driver covers which zip onto the boot cover. I think the answer is probably just to find an unclippable harness... anyone got anything suitable looking for a new home?