The next weekend (5/12-13) we accurately positioned the posts for the buildings (minus the rails) and added the joist supports around the bottoms of the buildings and some temporary framing above to keep the posts in position. In the process we discovered how difficult it is to get three long heavy boards level, plumb, and mutually orthogonal (perpendicular to each other) when none of them are permanently attached at either end! Then we poured the concrete for those holes.
On 5/19-20 we put in the floor joists (with some volunteer help from two carpenters) and positioned the rail support posts. Again temporary framing was added so the posts would maintain the proper position. Then concrete was poured in the post holes. Altogether 48 80 lb. bags of concrete were used to set all the posts. Fortunately we had a lot of help from the Boy Scouts (and Jim Mettler's Swiss Army Truck) for that! We also installed the plywood floor in one of the buildings that weekend.
Trustworthy, loyal, courteous, kind, thrifty, brave... and above all HELPFUL! Some of the many Boy Scouts that helped out. Together they mixed and poured over a ton of concrete.
Installing the joists.
A conduit was run under the floor to the pier for wiring.
Coarse mesh screen was used to keep the critters out.
Plastic sheeting was put under the floor to keep moisture away, and then 3/4" plywood was used for the floor.