Ken,

The regs no longer require the numbers on the wings, so they don't make mention of them. The original regulation was worded as follows:

"On airplanes and gliders, the numbers shall be displayed on the lower surface of the lower left wing and the upper surface of the upper right wing. The tops of the letters or figures shall be toward the leading edge of the wing. The height must be at least four fifths of the mean chord. If four fifths of the mean chord is greater than 30 inches the numbers need not be any larger, but may not be any smaller than 30 inches in height."

The regulation goes on to talk about other special circumstances, but the above quote covers what needs to be done on a Waco.

Hope this helps!

Joe
WB #54