You're own construction methods can have a big affect on where weight is on the model so simply stating an engine to be used isn't really enough to say.
You should treat each model you build (with respect to CG) individually. For .40 and .60 size aircraft, one of the best techniques is to build the model but don't secure the radio equipment (especially the battery) in position yet. Then set up a CG stand and move the battery and servos around until you get the CG where you want it.
Using the weight of the radio system itself for balance is the best way to save weight, and in the event you still can't balance the model with the radio gear, at least you'll have to use that much less lead to finish the job.

I just finished a .60 3D aircraft and if balanced close, but once the fuel tank was 1/2 empty, it became a hanful on landing due to the rear CG. A 1-1/2 oz. prop shaft weight is all it took to make it fly pretty.

Highflight