You have the vent on the fuel return line fitting
Sure do, if you are getting fuel on the floor from a vent line at the top of a half full cell, then you have your vent hooked to the return line location!!
There will be a line inside the cell attached to the fitting your current vent is hooked to heading near the bottom so when the fuel is returned to the cell from the bypass if used, it will not foam or drop in from the top, this is not the place for your vent. The vent location is only a hole into the top of the cell with no line on the inside. Always use a loop of your vent line above the cell before exiting the floor of your trunk to prevent sloshing fuel from coming out when it is full of fuel.
Bruce