I notched out the spars to accept the bracing. I also added some bracing for a third taillight. I also added a notch on the underside of the hatch to accept a cross piece/handle.
The triangular notch to make room for the countertop in the galley. Tight fit!
One assembly tip. I glued and screwed the whole thing together, but only loosely. Then I put it back in place on the trailer and tightened everything down. It was pretty loosey goosey at first. But pulling it together in place really helped it come into proper shape.