We will be using a steel piece to support the reciprocating floors (yeah, they aren't really reciprocating in a bearing sense of the word) and it will also allow the post below and the post above to have a good solid place to terminate.
There is 2 1/2x12's from Colorado, 7x14's rescued from a falling down pig farm, Douglas Fir logs from Montana, and a couple small beams from a barn in Illinois.
We are rabbeting the floor planking into the main floor beams so we can show the timbers and the design they are making.
The rim around the perimeter will be two rows of 2x12's sitting on a secondary bottom plate. While not necessarily essential, as we could have just used pressure treated 2x12 for the bottom plate, we thought it easier and quick during raising if the pressure treat was already installed on the concrete, on site, and then we could roll in and drop our floor onto the PT that we have squaring lines, if necessary, snapped onto it.
Keep in mind that we are fabricating this home in Montana and shipping and raising it in New York, so it is all about the most efficient and quickest raising possible.
