Your sheets already run outside the shrouds for either the lapper or the
genoa. I can't imagine how or even why to use barberhaulers on a P-19. Maybe
for the 'standard jib' though. You might look and see if there's a website
for some of the racing classes like lightnings. There might be a diagram of
how they work there...
Bill de Ment P-19 #779 'Wind Shadow' (now in Silverdale, Wa)
Eagle, Idaho (with 8" of snow on the ground!)