Hello, I purchased a set of plans for a new shed. As I was reading through it, the author recommends not to stack more than three 4 inch concrete pavers for stability.  

I took a string level and at grade at the highest point, to grade at the lowest point (measured diagnal, shed is 10 X 12) and came up with about 22inches. 

Now, I am trying to figure out the best approach for creating the foundation of this shed. There was examples of deck peirs but nothing on the max height recommendation when using them. 

The author does suggest for anything more than a moderate slope, to use concrete footings. I am thinking my slope is more than moderate on its lowest point.  With this slope, would I be best using a concrete (frost proof) footing? If so, should I use a sonotube? Or is it better to not use them? I figure I would not burry the post and use a bracket at the top of the foot for a 4×4 post to not have to worry about wood rot or anything later on. 

Secondly, this is a little side step from the thread question, but since we are talking about the footings, the author lists only putting support at each corner. So four in total. This is a 10X12 shed, and this person suggests using 2×8 floor joists 16″ O.C, end nailed and joist hangers. Should there be more support? I see all these shed building examples with concrete pavers all over the place on basic shed, and this author is only suggesting one at each corner. Should there be at least one in the middle of the shed? I have never built a shed before so maybe I am over thinking it. I plan on storing my john deere riding lawn mower, a snow blower, a push mower.. and whatever else I can fit in the thing.. So there isn’t a 1 ton car sitting in there, but I still feel like it’s a little light on the floor support.