I hate (I mean.. HATE!) these "flip a coin" things because I lose too many YGO matches due to my opponent's chance stuff wrecking my shit.
This said, I don't feel like this card needs this 50% thing. And, if needed, it should have a drawback, like, "If tails, it's reverse timed".
Or take it out at all. a 5/x card is already strong enough, since early game it would be 5/25+ at least.