I have seen many ship's assembly procedures that dictate the "non"
forked spar be inserted first, then the forked spar. This seems
counter intuitive (to me), and must be for a reason. Anyone know what
that reason is?

The owner didn't read the flight manual.

I know the owner (LS4-b) and he did read the manual. The manual does not
mention why.

Tony V. LS6-b