well high fps_min (such as 65.6) will make more fluctuations if the framerate ever goes below this number. what you didn't tell us is whether or not you tried any of the suggestions that were in my post. have you tried fiddling with time_smooth at all? i also like ulf's idea about v-sync. isn't the idea of v-sync that it synchronizes with the screen refresh rate? anyway, im not sure.
post us any findings coz i'd really like to know.

julz