Over the past several days have been working on the top skin area. Prior to moving forward with the top skin, I had to deal with the most forward top 4.0 rivets that go into the cowling strap. On both sides the holes were really far off on the side skins versus the multiple layers of firewall flange, cowling strap, etc in that area. After considering options, decided to enlarge the hole to a 4.8 countersunk rivet.
The next item to consider was the 3.2 mm hole on the top of the side skin. It seemed like it would be helpful to install a rivet there so the top skin fiberglass was holding all of the pressure down to form that corner. I considered upsizing the hole to 4.0 so that it would match the other 4.0 countersunk rivets over the top of the firewall but the edge distance in that area was too tight. I decided to put a few small shims behind that skin and use a 3.2 countersunk rivet. There was no pre-drilled hole in the firewall flange in that area so had to drill through the stacked layers behind that hole. The front top skin will go over this 3.2 flush rivet. I will also drill another 4.0 hole in that area now that the top skin is on and I can place the rivet in the same line as the others across the top of the firewall.
Trimming the front of the top skin was the next step by fitting and using some fine line tape to get the shape needed when it was strapped down. The front edge came more as a convex shape when it really needed to be more concave on the edges to follow the curve of the firewall. Some dremel cutting and sanding were done to get it shaped.
The next issue was that the right side of the front top skin as it went back toward the canopy was much higher on that side than the left side. Luckily the weather has been sunny and warmer so I set the top skin in the sun for a few hours to heat it up so the fiberglass would form better with cracking. I used a long level across both rear sides and added some significant weight on the right side to hold it down to as close to level as possible. Where the rear of the top skin meets the canopy there is a small bevel on the canopy that seems to be the approximate correct spot vertically so that the top skin side section is level along the side of the fuselage. I drilled some of the holes on the top of firewall and both sides of canopy with a hole finder where needed. The right side was wanting to deform slightly due to the downward pressure, but with some additional heating and gently pressing it down as I went along that side with holes/clecos it seamed to form correctly along the side of the canopy. Still have a few more holes to drill and to cut off the excess on ends by the canopy.