Hi guys, I an a newbe to gas engins so I thought I would ask the experts being you guys a header question. I have a Areoworks 50 cc Yak 54 with a DL 50cc engine. I know its not a DesertAircraft but this was a gift from a friend. I purchased a K&S 1060 tuned pipe and a DA header 25mm drop with flex. The length is 8.5" . Some good old boys at the field say I need to use the 11" header. After doing some measurments I found that a 11" header is way to long for the Yak using the tuned pipe as far as fitting everything in the exhaust channel of the Yak. The 8.5" fits everything just about perfect with a little over a 1 1/2" to play with. I like to get you guys input on this. I know I am completly lost on this. Thanks