Well, if you opt for the design correct CG location then you can easily get away with 25'ish % for the elevator. These models only get doggy in pitch when good intended builders insist on using forward "normal" CG locations on models that have more than enough tail volume coefficient to work with the CG farther back. The online CG calculators will give you the real goods on this.

On my larger size sparky.60 designs I've been very happy with around 40% area for the rudder with these running about 35 degreed of deflection. They get a little snappy when flying faster but for the slow power and glide portions this size gives a response much like a nice Gentle Lady glider. And that's very nice indeed. Both of the models I've done this with kept the original dihedral angles.

On smaller size models go with a LOT less rudder area. Or be prepared to hold the rudder deflection angles down a lot. Especially if you go for the original dihedral angles. If you go with less then you'll want the bigger size split. I had a Miss Tiny 1/2A Texaco model with a 40% rudder. I had to reduce the total throw to about 1/4 inch, or somewhere around 10 degrees each side of neutral. And even at this at higher speeds it would require gentle control inputs or it would stunt itself into tossing its kidney out.