My friend and long-time riding companion has been a gifted athlete for his 82 years. Of late, an ailment is causing him balance problems and he is ready to transition to a trike. We used to ride about 40 miles per week and he'll probably continue that regimen when he moves to hilly Seattle at the end of July. I have no experience with trikes but I would like to help him gather information so he can choose one that will suit him. I would appreciate advice.