I was planning on one circuit to go fore, top tapping for feed and bottom tapping for return and the same to go aft. There are four tappings at the back of the stove. The fore run is to have the header tank and the aft run to have a pipe venting outside, this will be off the feed and will vent higher than the header tank. I have tried to add a picture of the inside of my proposed header tank. If I have then the rest of my message may make sense if not then never mind. At the top left of the picture is an overflow pipe which I was planning on running into the return run back to the stove, bottom right of the picture is where I am planning to feed into the tank from the highest point of my feed from the stove, this is two inches from the bottom of the tank. I wanted to use these points because they are existing, welded fittings from my tanks previous life as a urn. I figured this was preferable to blanking them off and then having to cut new holes into the tank. Does this look feasible?