Have you thought about having your scope on a platform on wheels (with leveling bolts), and rolling it out of the shed for use Adam? I use a Ketter shed as it has its own floor (no lip to get over in the doorway) and wide outward opening double doors. My shed is on terazzo tiles with crusher dust underneath, with the tiles extending out into an observing pad in front of the doors.
Look
here for some ideas along those lines.
Having built one of these sheds in a few hours, I can now say it was dead easy, and it looks much better than any tin shed that I've seen. If you're renting, a drawcard is that these sheds can be easily disassembled and relocated to your next place should you move.
Food for thought anyway.
Dean