"Quite a few folks have pondered this through the years - myself included. Allow me to put on my Dr. Ruth field hat for a moment. Heinrich Mallison's concept of the African stegosaur Kentrosaurus mating seems plausible to me. I've assumed this myself as a default mating position for these animals. My read of the tail base in Stegosaurus is a bit different than Brian Switek's analysis. While it is true that our North American stegosaurs had limited up-down motion at the base of the tail, stegosaurs do something for ornithischian dinosaurs: they have the ability to twist their tails in a corkscrew-like fashion. I can envision a standing female Stegosaurus twisting her tail to one side and therefore removing obstacles for her mate. Unlike the boated models in your photo, a living Stegosaurus would have been able to stand and even walk on its hind-limbs with grace. So, therefore I see no barrier putting a male into mating position. So, there you have it."
There we have it indeed! I hope you find that enlightening, as well as the video! The dilemma definitely makes more sense after hearing what Mr. Mossbrucker has to say!