I used eggbeaters and I stay clipped in while doing trackstands at red lights all the time, it’s just one of the perks of riding fixed. In the rare occasions that I’ve lost my balance I was able to unclip in time(yeah after saying that I’ll probably fall down today on my way home ) Like Stevo said, just practice more. If you’re having problems doing a trackstand unclipped, (needless to say) doing it clipped in is just asking for trouble.