I have been having calf problems and it is mainly due to ankle flexability. The problems started one I started using nike lunar fly's. I have used thelunar series before and had no problems. I am a forefoot striker. I am looking for a shoe with a miniumal amount of heel drop to get my ankle moving more. I know this will cause problems to begin with. Is 1mm of heel drop make a difference? Will i notice a difference between like 9 and 8mm drop?