Putting the tank just ahead of the C/G is what my Northstar has. You hit it right on the head when you mentioned that you can take almost a pound off the weight. I have gone so far as to have mine balance right on the step and it flies great. It cures one of the criticisms of the North Star having a soft elevator. I used the Perry diaphram pump mounted just behind the firewall and ran 1/8" hard nylon tubing for a fuel line from the tank compartment to the pump. Just hold your finger over the venturi when starting and release it when you see fuel starting to come. Runs are very reliable, good idle and top end. A Supertiger 51 motivates mine.
Peter I hope this gives you some ideas Newc. Thanks, Bart (man)