I wrote something similar to this (well exactly but I am tired) in a post but thought it might be interesting enough to have a post of it's own.

A source of good information was a government document called DATCOM. I forget what the word means. It allows you to go through all of the steps to determine the airplane characteristics. I spent way too much time with it back in the '60s doing manual calculations.

An electronic version of it called Digital Datcom as well as other programs of interest can be obtained here for $295. I think there is a lower price for students.

http://www.pdas.com

Being old and retired I begged for the student rate which is $99. This might seem pricey but the ability to analyze a design seems excellent. There is stuff on shock waves which don't have much application to a park flyer but otherwise it seems good.

Anyway I have ordered the CD and will give an assessment of it after working with it for awhile. It would be nice if there was an equivalent but aimed toward the average modeler and at a more reasonable price. Although at $99 it might be worth it if you are getting ready to fly your dream airplane and have no idea where the CG really should be.