I attached the shims I had made earlier to the HS with double-sided tape. I placed the HS on the tailcone and clecoed it in place and then drilled the #12 holes and bolted the rear spar to the attachments. Next, I cut the spacer block and positioned it between the forward attachments. I measured the HS as shown in the instructions and it turned out to be correct without requiring any displacement of the spacer block, so I clamped it in place, rechecked the measurements to insure I had not moved the HS, and then drilled the four holes through the attachments and shims before stopping for the day.