According to Wiki, "the stripes were five alternating black and white stripes. On single-engined aircraft each stripe was to be 18 inches wide, placed 6 inches inboard of the roundels on the wings and 18 inches forward of the leading edge of the tailplane on the fuselage." A P51 has a wingspan of 37 feet, an RV-4 has a wingspan of 20 feet, so the stripes would need to be 9 3/4" to represent the same proportions. To be really authentic I understand you shouldn't mask them neatly, but just paint them hurriedly with a big coarse brush!
Chris
