Ray (minnesota modeler) has posted pictures of a set up that uses notched fuel tubing that goes around the tank and the notch is at the bottom.

Do I like did on a couple.  Drill holes to fit tubing, kind of a force fit.  Then J-B Weld inside as well as out.  DOC Holliday

            Tom , I tried using the older vented stunt tank with the metal baby bee back plate. I used very small fuel tubing with dowels jammed in the ends to cap off the baby bee fuel nipples. This didn't work too well for me. The tubing would always pop off for starters and I don't think it was completely air tight. I never got a full run from this. I think Jb Weld would do a better job of blocking those nipples. I saved a lot of the backplates from the plastic model engines similar to those on the production engines. I found using these with a small tank gave me a whole lot less trouble. Some of the needle valves on some of my backplates had some very fine threads which suited bladder usage. Ken

Hi Tom, sorry I just now found this, I don't usually check all the forums.

If you just cap one of the vents after filling, it will work sort of like a uniflo, and won't lose any fuel inverted since it's drawing air through the single vent.  The notched fuel line looping around the bottom really didn't work too well, hard to keep it on the vents. Best is to use an external tank of your choosing.  You can drill a hole through the side of the integral tank and install a fuel line to the nipple, or buy a Cox production engine ($8?) and use its backplate.

--Ray