You don't have to hope or even cross your fingers, just measure the sucker with a yardstick and you can easily find out exactly where the CG should be. It takes the size of the tail into consideration and how far back it is or isn't.

You make 9 measurements. Most modelers can measure stuff pretty accurately. Then you type them into an online workpage and mouseclick. Scroll down the same page and read out the CG location. Oh yeah, you have to type in the number "5" before clicking. So, you look for the CG location and write it down, then change that "5" to the number "15" and mouseclick again. Look for that CG location and you've got a safe, reliable CG range for your exact airplane. It's the easiest method around. And it uses the same formulas the aeronautic industry uses. Only you don't have to do any math, it does it for you.

http://www.geistware.com/rcmodeling/cg_super_calc.htm