There are no knee braces, but otherwise you are on the right track.  I didn't mention that the rounded pieces are 1.5 x 4 inches and on 2 foot centers.  Suppose a 2x4 or 6 horizontal above the loft floor a few feet would be OK or would something like a roof truss be better?  If I could work off the floor and do the work before the floor came out, that would be great.  Thanks, Ben