Saxat från: http://www.formulawindsurfing.org/filez/article/041128/RRS2005-2008.pdf (sid 100)
G1.2 Specifications
(a) National letters and sail numbers shall be in capital letters and
Arabic numerals, clearly legible and of the same colour. Commercially
available typefaces giving the same or better legibility
than Helvetica are acceptable.
(b) The height of characters and space between adjoining characters
on the same and opposite sides of the sail shall be related to
the boat’s overall length as follows:
Overall Minimum Minimum space
length height between characters and
from edge of sail
under 3.5 m 230 mm 45 mm
3.5 m–8.5 m 300 mm 60 mm
8.5 m–11 m 375 mm 75 mm
over 11 m 450 mm 90 mm