With the spacers fabricated, the next step was match-drilling the spacers and tiedown plate to each spar. Some other folks have had problems getting the spacers aligned between the plate and spar. My approach was to mark two vertical lines on each spacer, each one halfway between the center hole and the left or right side. I then aligned and taped the spacers to the spar so that the vertical lines were centered in the spar holes to be used for match-drilling the spacers to the spar and tiedown plate

pacers in place

Here’s everything clamped/bolted together, ready for drilling.

Tiedown in place