Alex replied:

Mike, I don't know of anything like what you've asked about, but assuming you'll only have a light load up there it may be worth considering a system I saw used to mount solar panels on the roof of a poptop. This consisted of bars made of square tubing with larger 'feet' on the ends of the legs (about 3inches square/75mm) which were screwed into the fibreglass roof of the poptop and sealed with silastic. Of course, to use this system you have to be strong enough to lift the weight of the roof and kayak all at once!!

Alternatively, a system I use to load a canoe onto a high roofrack (not on a poptop) is simply a slide-out bar at one end, so I can lift one end of the canoe onto that and then pivot the other end onto the rack, than put the first end all the way on. If you can mont bars out of the way of the poptop, two of these will enable you to slide the kayak out of the way to lift the roof. Couple of ideas here, hope they help you. Cheers, Alex.