NOTE: The fuselage was still inverted during this operation, so the pictures look upside down.
Fitted the spar box into the fuselage. This is a lot of drilling and aligning, but really not that hard. There are pilot holes in at least one side of every hole that needs to be drilled, so it's really just making sure the parts are aligned properly, clamping them tightly, and drilling.
For the front and rear box halves I drilled and attached to the floor first, to make sure they did not shift vertically. I then clamped and dripped to the side support members. The upper angle was then drilled and attached (turns out I later had to redo this...).
