RE: Kat 40 Dude!!
For lateral balance, as long as I think it is within the width of the fuselage I like it.
Some say to hold the crankshaft (off compression stroke) and the top of the rudder and hang the plane to watch for a wing tip to consistently dip.
I just put my fingers under the fuselage, one fore one aft, and see if I can balance it for a few seconds without too much work. If I can, it's close enough. A precision pattern machine might need a stringent lateral CG, but these planes fly well, even if only "close enough".
Some folks like to do that upside down too. Some say with a partial tank of fuel. Again, it is not a super critical measurement.