Question: How much engine power is appropriate? Many models give a range of engine sizes... should I use an engine that is at the bottom of the range or go for broke and use the biggest engine recommended?

Answer: If in doubt go with something that is more or less in the middle of the range unless the distributor or your dealer have some specific recommendations.

DO NOT use an engine larger than the maximum size recommended by the model manufacturer. You run the risk of overstressing the airframe which can lead to sudden breakup of the model in the air and may injure someone.

Better Answer: Generally manufacturers specify a range of engine sizes for a model. An engine in the middle usually works well but you might want to consider going with the higher end of the range if you are going to be flying at altitudes above 2000 feet or in very hot weather or flying off of floats. Naturally if you are doing all of these, flying at high altitudes from a lake on a hot day... the bigger engine is the better choice. You might also want to ask around in your area to see what other RC flyers are doing. Be a bit cautious of the "power at all costs" type of recommendations but listen carefully when you get advice from those who have thought it through and tried it out.