Just wondering why you would mount the tank at the CG without a pump on the OS engine - or are you saying you'll must mount tank at firewall?

I only have experience with one plane having the tank moved back to the CG, and it is so much better. Think about the change in balance from a full 12 or 16 oz tank or whatever going from full to empty. I notice a big change between the way my plane flies at take off versus when it's landing. Perry pumps work amazingly well and are only $30.