Can you please supply more details of the model?
Pics or a descrpition.
Is it a Semi Scale ? Radial? Ducted Fan? Biplane? Sports Model?
What wingspan? Motor Size?
What sort of motor have you got installed? 2 stroke? 4 stroke?
What is the all up weight of your completed model?
Many semi scale models of short nosed, radial engined airplanes, such as AT6's, Mitsubishi Zeros etc, need lots of ballast weight up the front to get the C of G right.
I have seen scale models of the Hawker Typhoon, powered by large 4 stroke motors, with over 1.5 pounds of ballast up front.
It's just something that the owners have to live with and if the model, with ballast, is still within the accepted weight range of the motor's capability, it's no big deal.