Just about finished with my Pulse XT build and I will have to balance it tomorrow. Should I measure the CG with the fuel tank full or empty? This is the first plane I have built in about 12 years and I just don't remember how to do it correctly! Thanks.

You should measure the CG with the fuel tank empty. That way when you take off with a full tank you will be a little nose heavy but when you burn off fuel you will not go to a tail heavy situation which is usually very bad.

The only time you would do balancing with fuel onboard is if the tank was located aft of the intended CG point. This happens very, very rarely.

The filled tank would be used for a Seawind, Arrow and Northstar, wouldn't it?

I'm not familiar with their tank locations. If the tank is aft of the CG I would expect the INSTRUCTIONS would call for balancing with the tank full. The INSTRUCTIONS are always your first point of reference to follow.

If the tank is located directly on the desired CG, it would be irrelevant.

The Northstar and Arrow are both delta wing flying boats with the engine and tank in a pod in the middle of the vertical stab. There are no instructions as they are built from plans, though there is a lazer cut kit for the Northstar on the market. I'll have to do a little digging in the Seaplane area to get more info on them

Sounds like the tanks are aft of the CG on both described. I would think balancing full would be best. This way the balance (CG) would shift forward as fuel is burned.

Great. That is the conclusion I came to on my own but I have learned not to always trust my own conclusions!. I just wanted to make sure that the instructions weren't being vague in that very im portant area.