Hey guys...I'm working on a H-9 p-51 too and I'm gonna use a Perry v-30 regulating pump...This way, I don't have to pressurize the tank, and possably have a rupture (painfull!) I don't know for sure if they work w/4 strokes tho...I read that you can use a T fitting in the pressure line( goes from the breather nipple to the pump, w/ the third line vented to atmosphere) I'm using a 2 stroke...A friend used the Perry pump on his O.S. .61FSR (this was back in the mid '70's when they first came out) in a Dirty Birdy, w/ the 16oz. tank mounted over the C.G. and once he got it tweaked right it ran beautifully! I've been using them for the same ammount of time, and dang if they aint great! Like djlyon sez, test your set-up by running the engine, and then point the nose straight up to simulate the attitude(s) models sometimes get into...See if it goes lean (I'd be supprised if it doesn't) And w/ 1/2 a tank too...Like Danny says, you might want to use the bigger tube too(wazzup Sup?) Good Luck Smitty, let us know your findings...