Then soneone posted picture of the red vented cap and you said:It has the red vented caps with the small holes inside them when you luck at them from bottom up.
So, the question is, how is your system vented?The caps do look like that except they are solid (the two holes are not present).
Bottom line: if you do not have a vent line that connects the air spaces of the two tanks then you cannot have a valve that allows fuel to be drawn from both tanks at the same time. The plane would be in an "unairworthy condition."
Remove one of the forward wing root fairings and look up in there for the tank airspace interconnect line. If it is not there you need to get a valve that doesn't have the "Both" position.
