I picked up some white vinyl at a local sign shop to make the aircraft registration numbers for the vertical stabilizer. I also designed some "Danger" arrows for the tailrotor. I used the guidelines for the N-numbers found in the EAA Homebuilt Registration packet I bought from Aircraft Spruce. The info packet contains the registration documents you will need to register and have the airworthiness inspection done on your homebuilt. The kit also gives the specifics on size, font and spacing of the N-Numbers.
After sizing the letters in a drawing program (I used CorelDraw) they were cut using the laser. I used the wet application method (same as the main rotor blade tape) to make it easier to position the numbers.