Spark Plug Gap Tool and Feeler Gauge

Good topic - like you I have all the gear needed to gap single electrode (traditional) automotive style plugs but nothing for the the latest Rotax recommended ones.

You shouldn't need to gap the new Rotax plugs. NGK's, yes.

You need a wire type gauge, something like this one at the link below.  
You are measuring gap “SP-01” in the attached diagram. Of course, you gap both sides. 

https://www.zoro.com/proto-spark-plug-gap-gauge-set-j000k/i/G7499703/?utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=free%20google%20shopping%20clicks&gclid=EAIaIQobChMIkOmUw_j3-wIVdRKtBh3IbAzjEAQYASABEgL5oPD_BwE

Thinking about this (for the first time) I don't see how, the home mechanic, can gap this style of plug. Bending the electrodes will change the alignment of the "tongues" to the centre pole and likely cause accelerated wear - I'm with Roger on this.

You're not supposed to gap the Rotax double electrode plugs. You put them in right out of the box. Then when it's time you're just supposed to clean them and put them back in. Rotax has these made for their specs.

NGK single electrode plugs are gapped at .030 out of the box and need to be gapped before you install them. These aren't made to Rotax specs out of the box.

Bottom line, leave well enough alone.