I've shot a few rolls through a couple transition 500C bodies (the ones that were marked as 500C's but were actually C/M's). I've yet to experience the "bullfrog" effect. If it's that big of a deal, there is a tab just below the wind crank (or knob, depending on your persuasion) that is the mirror prefire. Hit that, and take your shot. To me, it feels no worse than an FM2n or a Nikkormat FT series body. If anything, it feels more damped.

-J