Having just read the SPL's handbook (great read btw), I encountered the uniforming section on page 32, after which it became apparent that a troop hat is acceptable wear, per BSA uniforming regs
"The Scout Uniform can be a source of pride and spirit. Many Troops have a special neckerchief worn by members, or a hat of a certain color or style. A troop's activity uniform may include a T-shirt emblazoned with the troop's emblem or some other signifigant reminder of the troop's identity."