i am planning to do this mod for my xl sometime this week
i wanna make sure i got the parts right

one way valve
http://www.greathobbies.com/producti...rod_id=YSE0405

t fitting
http://www.greathobbies.com/productinfo/?prod_id=ROB218

pressure fitting
http://www.greathobbies.com/productinfo/?prod_id=DUB539

just wondering why do you put the one way valve from between the t valve and the tank cap, instead of between the t valve and the pressure fitting?
thanks =D