Step 1: Making a Template
I laid the wax paper over the tank and taped it down with some masking tape. First I marked out the hole for the fuel cap.
Next I placed on hand on the center of the tank and slid the other hand down the wax paper until I went passed my desired decal size or the wax paper started to bunch up.
Marking these spots allowed me a general idea of the limits for my decal. This allowed me to draw a smooth shape for the outline of the decal.
Step 2: Applying the Template to the Decal
Since my Union Jack is 4 parts on a red background I was able to make it larger than if it were one solid piece. In making my template I tried to account for the spaces between the decal sections. This also meant that the sections didn't need to be exactly the same size since it wasn't symmetrical.
With this in mind I laid the template over the decal to observe how it was best suited to the tank and the cut. Once I decided on the decal layout I cut it out.
Applying it was the hard part. First I cleaned the tank. Then I peeled off one of the quarters and sprayed a liberal coat of Rapid Tack on the decal adhesive side. This made it much easier to apply to the tank and maneuver into the desired position. I did make a small mistake in trying to cover a chip in the paint. It upset the alignment of my decal. It didn't cause the decal to wrinkle or bunch though so I am happy with the result. I'll fix this in the next version.
Thanks for reading.