All tips fit 4,6,7,8 and not sure about the 3 and 9, but i think so.
W415 is your tip. That's the original 6 tip. A great tip. When cutouts became the norm, the tip went to w715 (batwing) and then w715-1. There is a slight drag component with the old style nav/strobe/position lights, but I'll bet you can't make any meaningful measurement of it.