I would also make sure to seal the bottom up well when mounting it to the base. We neglected that and now I'm fighting moisture issues in the bottom. Waiting for the weather to clear up and then I'm going to have to empty it out, clean it and seal it.
Placed vertical vents in mine as the panels run vertical to keep the structure as intact as possible. I had to cut across one of those ridges for the pop door and it definitely takes away from the stability of the wall.
For our base we framed out a floor like you would for any shed with...