Sailplane fliers and fun fly model types often use the Dive Test to set the CG very close to the true neutral point. This has been described often in the past in the Gliders and Sailplanes forum. Try doing a search for it.

It's nice and safe because it let's you sneek up on the optimum CG point rather than guessing.

There's also some formulas that relate the Tail Volume coefficient to the wing to determine a good CG starting point in this thread....

http://www.rcuniverse.com/forum/tail...1547609/tm.htm