Tonight, I finished cutting out the hole for the fuel tank filler cap of the left auxillary tank. I was able to use the template I created for the right aux tank filler cap. I simply flipped it over, opposite-hand. This is benefit of making the template out of aluminum sheet. By now, I've got quite a scrap bin going. To drill the hole for the tank filler cap, I used a 2.25" hole saw I had used to install doorknobs in our house. The hole should actually be a little larger than that, but this works out well, leaving a little extra material to grind off, leaving a perfect hole. Backing up the hole saw with a piece of wood is a necessity though, as the saw wants to wander without it.
Wood backup, held in place with clecos.
The bit warbled a little. Good thing there's extra material.
