Thanks for the help, I have other models setup w just the two lines. This model uses the smaller header tank behind the firewall so a larger tank can be placed further back in the fuselage where there is more room. The header feeds the motor, the pressure tap from the motor pressurizes the larger main tank (further back in the fuse) through its vent line and fuel is then pushed from the main tanks clunk to the headers vent line thus filling the header. Clear as mud? Fueling gets tuff because you have to push fuel past the header into the main tank. I'd get a single tank for the nose, but I don't think I can get 40oz up there