Hey Cambo,
Walbro and Zama carbs have built in pumps, so you can place the fuel tank on the CG. I will run 1/8" Tygon to the BCMA 40cc gasser for my Cap, with tie-wraps or Dubro fuel line clips at all connections. I plan to start with a 16 oz. tank and see how long I can fly on that, and it will probably be too big. I will loop the vent line to the back of the tank and forward again to exit near the firewall so fuel does not siphon out when the nose is down. I run a filter in the vent line so dirt cannot be sucked in on the ground, but it may be overkill. Also, I have soldered a piece of 1/8" copper tubing over the hole on the carburetor metering diaphragm cover, and I will run Tygon from it through the firewall so that pressure inside the cowl does not affect the fuel mixture. Hope this helps!
mass balance