If you are using original panels etc and not going for a full decal set then I think it is in keeping to try and match the original YAMAHA letters on the swinging arm.
First up was to wipe the swing arm with brake/clutch cleaner to make sure it was grease free. I then located the decal where I wanted it with some masking tape.
The advice on the fitting sheet that came with the decals was to use the "hinge" method. This meant putting a strip of masking tape across the top of the decal as shown below.
Next, lift the decal "flap" and peel off the backing paper carefully. Some of the letters may try and come off with it but they are easily persuaded to stay on the clear sheet
Very difficult trying to take pics of some of the stages as you ideally need three hands! The next step is to stick the relaining sheet to the swing arm being careful not to trap any air. A lot easier to do than explain.
Then peel off the top vinyl layer leaving just the letters firmly stuck to the swing arm.