I'd be painting the joiners or replacing them with black ones as well as that mesh in the side vents. Bleck. Anything that's bright that sticks out all shiny like is counter to the concept of a military theme.
I have about 3.3m slab to rafter gap at the lowest point and if the outside height of the slab the shed it on is consistent across the width I have roughly 210-225mm. Should be pretty okee dokee, yeah?
Super keen on a hoist for my shed too (was always my plan. Will check concrete thickness.
Found this which furthers the 100mm mentioning by that crazy Lotus massive shed owning man.
http://www.autohoist.com.au/two-post-car-hoist-safety-bar-spreader-bar.html
In use