You should always balance with an empty tank. A lot of guys recomend a litle nose heavy , I don't.
A little nose heavy makes it more stable but also makes the elevator less effective. Plus a tail heavy airplane has to land faster as it will have a higher stall speed.
I think you should
balance it in the center of the recomended range as a good starting point. Then if it gets to sensative as it burns
fuel move the C.G.
later daveo