I am working on an application that displays surface winds. Wind speed and direction will be displayed using "wind barb" symbols, as described here: Plotted Winds

My question: Are there any standards for the angles and lengths of the "flags" in relation to the the wind-barb "pole"?

Eyeballing the diagrams I've seen, I think that an angle of 60 degrees and a flag length about a third as long as the pole length would look fine, but if there are any officially defined standards for these symbols, I'd like to follow them.

Note: This app will not be used for navigation, so it is not very important that it look exactly like an official chart. I just don't want it to be ugly, or to look obviously wrong to a knowledgeable user.