I'm a southpaw, and recently I've started trying to utilize my left high kicks more. Unfortunately, it seems like every time I spar a taller opponent and try them they end up being awkward and without power or I end up off-balance. I don't think it's an issue of flexibility, since I've got a 170-175 degree range of motion, and I never have trouble kicking at head height or higher with power on the heavybag, so I don't think it's an issue of poor technique. Maybe high kicks just don't work on opponents that're taller than you? Or am I missing something here?