i don't strap in very tight. i would on rides where i don't expect much traffic, except i hate ****ing with those things. i like being able to pull my feet out if i'm falling. i actually like clipless best for that, but i have to re-buy a pair of pedals after getting rid of my road bike...

anyway, my point is that even if you don't need to take your feet out most of the time, you will if you fall, so even if you don't tighten them, you'll lose a slight bit of power across the bottom, but with the right pressure, you don't need to lose all power in any section of your spin. practice, control, etc--as with many things on a fixed gear.