Next I countersunk and deburred the bottom cowl hinges.
There is not much clearance between the bottom firewall flange and the engine mount tubing for riveting the lower hinges in place. I should have riveted these hinges to the firewall before bolting the engine mount to the firewall. Oh well, I'm not about to remove the engine and engine mount just to set a few rivets.
What worked for me was the tapered no-hole yoke with a small piece of steel taped to the surface to provide an offset. This allowed plenty of access to sqeeze all of the rivets without mashing any of the eyelets on the hinges.
Bottom cowl hinges countersunk
Tapered no-hole yoke with small steel spacer taped to it to clear hinge eyelets
