With the upper empennage fairing almost complete, I started installation of the lower empenage gap cover F-794A. This is an aluminum strip with a rubber strip to seal the lower empenage opening between the side of the fuselage and the horizontal stabiliser bottom skin.
I had installed too many rivets in the longeron so I had to drill these back out. I'm quite good at this and was able to drill them out without enlarging the holes. My technique is to start drilling the center of the rivet with a smaller size drill bit. It makes it easier to center on the little mark in the center of the rivet. It also allows to drill deeper than just the head of the rivet without damaging the sides of the material below. Later on I drill the head with #40.  Inthe image below you can see that center-drilling.

Then I matchdrilled the fairing to the longeron. The top of the fairing will need to be sanded of worked with the die grinder deburr wheel to remove some material so that the rubber strip can be installed.

Both sides drilled in the image below.

Next I drilled and enlarged to #36. The longeron needs to be tapped for a #6  6 32 screw.
I countersunk the F-794A. I used an aluminum backing plate with a #6 hole so that the countersink bit would not wonder around (resulting in an ugly hole).

The strip is very thin so the hole will be enlared and it gives the impression of a poor design. But after all, it's just a cover.

 When countersinking is done and the strip moved, you clearly see this material is too thin to be countersunk. The Section C-C on dwg44 clearly shows it has to be countersunk so I'm not going to question Van's decision on this.

 Finally, also drilled the last 2 holes where they are in assembly with the elevator horn access cover plates.

I used a set of washers and a #6 screw to locate some nutplates on the inside and drilled the nutplate ears in the F-709 bulkhead.

drilling done...