It depends on the the weight of the aircraft. A rule of thumb of 10cc to .60 sounds fine for lets say the U-CAN-DO plane. But for a warbird with ignition battery as OPJOSE has stated you might want to go as high 20cc or 26cc. It really depends on the model. Look at zenoah or fuji.

Also since you are in Kansas the elevation doesnt play much into your decision. But the higher your altitude the more engine you need.