FAA REGULATIONS
The following are the FAA regulations as they apply to Experimental Aircraft.
Up to 180 Kts C.A.S.                                           3"
Faster than 180 Kts C.A.S.                              12"
*Aircraft 30 years or older                                2"
Registration Marking Size          Minimum
Registration Marking Placement
Experimental Aircraft 2" or 12" Markings
   
Horizontally on the:

                         Tail; or
                        
                         Fuselage between the trailing edge of the Wing and the leading edge                                of the Horizontal Stabilizer; or
                        
                         Jet Engine Nacelles


Experimental Aircraft 3" Markings

Horizontally on the:

                         Tail; or
                        
                         Fuselage between the trailing edge of the Wing and the leading edge                                of the Horizontal Stabilizer
                        
  Vertically on the:

                         Tail
For more infornation read 14 CFR 45