Greg Reid wrote:

Thanks for the suggestions so far. I had already considered both of
them:

1. Filling on the ground, and gravity draining in flight

For optimum "go fast" trimming, I really need to be able to transfer
fuel rearwards in flight, once at altitude. The plane will fly
fastest and most efficient when trimmed so far back that it's unsafe
for take-off ... or anything but fairly straight-and-level at high
altitudes. I'll want to pump some forward again as I'm decending to
land. (And no, I'm not crazy enough to go WAY back out of the
envelope.)

OK, what you're planning to do sounds fairly dangerous. It sounds like
you're trying to shift the W&B during flight so that the horizontal
stabilizer is generating upforce instead of neutral or downforce (that's
why the plane goes faster: less thrust goes into making induced negative
lift on the horizontal stabilizer). Stalling the upforce-producing
horizontal stabilizer before the main on a conventionally rigged aircraft
would be about as much fun as stalling the main before the horizontal
stabilizer on a canard. Normally, stalling the horizontal stabilizer on a
conventionally rigged aircraft is no biggie. Since the horizontal
stabilizer normally produces downforce, stalling it makes the nose pitch
down, which causes an increase in airspeed, which unstalls the
stabilizer. But if you make the stabilizer produce upforce and then stall
it, you're in a deep stall and a world of hurt.

But to propose another solution to your original question: plumb a manual
on/off valve in parallel to the checkvalve-equipped pump from main to aux.
tanks. Want fuel in the aux? Turn off the valve and turn on the pump
until you reach the desired fullness, then turn off pump. Want to take
fuel out of the aux? Open the valve until you reach the desired
emptiness, then turn off the valve.

Russell Kent