I'm in the process of building a Sig Somethin Extra and have a couple of questions. I've only flown electrics so the nitro engine is new to me.

First question (and a stupid) - When you measure the C.O.G. do you leave the tank empty or full?

Second question - I've narrowed down engine selection to Irvine .53, O.S. .70 4 stroke, or Saito .72? I would rather spend less than more obviously.

Thanks,
Chris