What am I doing wrong with this bed install?

[jcwren]

Got all the boards position, cross sills in place, dropped the front end of the bed on to the perches, went to drop the back end, and its high centering on the floating sill.

I have a total of 6 cross sills. The one closest to the cab, 2nd is at the next set of bolt holes back, 3rd sill at the 3rd bolts hole set, floating sill at the 5th set, 4th sill at the 7th set, and the 6th sill at the 8th set (not counting the bolt holes that go through the piece of angle that's attached to the head plate).

It doesn't appear to make any sense for the floating sill to be anywhere else, otherwise there's a long expanse of no support.

I cannot find a single dang picture on the intarwebs that shows how these ought to be arranged, and nothing in the FSMs that I can find.

(Not sure why the pictures are rotated, they're correct on my phone and on the PC).