The SS plans call for building an insulated platform of 2x4's with plywood on top and bottom. This platform can be fastened to a trailer or attached to three 2x6 girders which rest on concrete piers. Since my SS will be used as a shed, I don't need the insulated floors and I would rather not go with the big girders. I am thinking instead of building a platform with PT 2x6 floor joists which will rest directly on 9 concrete blocks. I'll put 5/8 ply decking on the top and leave the bottom open to breathe. This appears to be how most of the 'better' sheds are built in my area. (Some are just 2x4's on blocks.) I will put two 8x16" pavers under each concrete block. This will increase the block's footprint to distribute the load over a larger area. I can also add additional pavers to help in leveling the 'foundation'. My lot slopes about 1 foot over the 15 foot length of the SS, so it won't be too difficult to level it.
I wrote to Stephen Marshall with a few questions that I had on the roof panels. He emailed me back with answers right away. I'll explain more when I get to building my roof.
I need at least 1 window that opens in my shed. I see that Lowes has a vinyl single hung 24x38 inch window for $100. That should work for my needs. The cheapest window I saw at HD was $150.