Thanks guys - All is well with the fuel pump!
I took the 29U on several test drives this weekend and the pump is working well, and not overflowing. I am amazed that the Kingston Vac Pump does not have any check valve to prevent gas from being drawn into the oil pump. It appears Chet is right - the system is in balance somehow with a well vented gas tank.
I put new gaskets on the old original gas cap, but ensured that the cap vent was well open. The gas tank does not appear to be leaking any at the cap or gas gage, so all seems well and good.