Capt. Ron,
As the guy said before not all ARFs are built exactly the same. Depending on things like the materials used, the engine you install and even the way you built it. The practical thing to do is set it at the recommended CG then go from there.
That being said I ended up setting the CG a little forward ¼ in. Just to be safe I would recommend setting it forward just a little to make sure you can land it, and then go from there.

On this plane I found that incidence is just as important (if not more) as the CG. Make sure you check the incidence of the Upper and Lower wings and the horizontal stab, they should all be “0” to each other.
As I mentioned in a previous post if I had known that the incidence on the Upper wing was going to be off I would have adjusted it while I built the plane. I ended up using shims to solve the problem.
In this scenario I would recommend attaching the Lower wing in the saddle, level the plane until the wing is at “0” incidence then install the horizontal stab. Set it to “0” (while gluing) then do the same to the Upper wing.

I spoke to someone who also has a GPSS he had the foresight to use an incidence meter when he installed the wings. A practice I indent to do when building my next planes. He said he had to adjust the brackets and force the Upper wing into the “0” position before attaching it with the screws but when he finished if flew with no problems.

The last thing a would like to say is; I mentioned the engine before because that could throw off the lateral balance of the plane. I always check and adjust the lateral balance. I would rather do that then to add in a lot of trim in the air to make the plane fly straight.
You may or may not already know many of the things that I said before but I hope this helps.
Good Luck,
Shubova
[8D]

PS: You have been threatening to build that thing for a while! [sm=biggrin.gif] LOL…get ’er done!
Believe me it's a great feeling when you see that baby fly! It is sweet! It gives me goose bumps just thinking about it.