I know a fair number of math teachers. They should be able to figure it out I suppose if they are willing to tackle it.
The problem with using someone else's Hullavator is that the rivets holding the cylinder on will have to be drilled out and replaced with something less aesthetically pleasing.
Replacement cylinders aren't that expensive from MCmaster-Carr--about $24 each with the fittings.
You're right about Thule. Most of their stuff is very expensive and the Hullavator especially. But for people with back or shoulder problems or high vehicles or short people, they are quite useful.
Classic Freestanding Rack
Dock & Launch Systems
Wall Mount Boat Racks
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