The Head On Pass is a legall tactic,wether 3 on 1 or 1 on 1.
I recently read a report from a P-47 pilot at Wright Patterson Air Force Museum.In the report he tells how himself and his squadmates encountered 50 + 109's at 20 -K.
He says he made a deflection shot after flying straight at the 109.
The german pilot took the shot as well,for the 47 pilot says he had 2 guns left and his K-14 Gunsight was damaged.He says he rolled over vertically and came down upon the 109 and put a 3 second burst from the white cross all the way too the cockpit.
He reported seeing no chute come out of the plane.
The HO pass is a legal tactic,an easy tactic.Mind you that i do not prefer the HO,I myself like going for a 6 kill,it's way harder too get too the 6 position but easier too kill them from the 6 postion.