You can calculate tail volume, and see exactly what would be acceptable fin area for your given wing area/tail moment. This holds true for the stab/elev area as well. Generally, stab/elev area on CL planes is more than needed for RC.
I am of the opinion that with such small radio equipment available to us now, "fattening" up an older design would not be necessary. One thing to keep in mind would be to keep your aircraft light, as the fully symmetrical airfoils will not be very forgiving at slow speeds, like landing. Of course, a little washout would not hurt, if needed.