I remember when photo-bucket was not a piece of hairy garbage, as does pepperidge farm.
I would design it with 1 4 ft section of 1" PVC inside the next size up, so it's adjustable, for the forward portion. With strong, coated metal brackets on the end to secure the underside and to not intrude into the space you need to mount it to the car.
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For the backside, I would use perhaps two shallow, flat hooks like that of a gun rack, to hold the rear. I had toyed with the idea of flush-mounting some high strength, semi hidden rope mounts or hooks into the blank quarter of the hardtop, but I haven't tried it yet.