I find it quite wierd that your best chao is a tails chao, and he lacks a lot of flying power...
Same with your knuckles chao. Both lack the needed atributes for their chao type. Although it is possible that you just used the minimum amount of flying skill to get your desired result.
I started my liking for this game at an old friend's house. I wanted my own chao to take care of and poof! I have a file! My first and greatest chao was Joey. In his first year of life, I wanted him to be a dark chao. When his tranformation day grew near, he startd to turn green from his normal dark skin. We started panicking and furiously started petting him with Shadow and nothing worked. When he finally went into his cocoon and emerged a Shadow chao, my friend was yelling "A Shadow chao!? Lucky! I never got around to making one!" And soon, he had a Shadow chao all to himself.