Should work fine assuming you time it right. It's best to go for when they have based out on you from mount or even have their hooks behind your thighs from mount. However it is very hard to take clear pictures with someone else lying on top of you. Assuming you don't put the foot too high up their body or too far across you won't get heel hooked.
Jin'emon, I escaped from Murilo Rupps mount with this escape and seeing as how he is an American Top Team black belt instructor I think it is safe to say it can be achieved against someone that isn't lobotomised. Apparently Roy Harris also uses and includes this technique on one of his tape sets (Smorra commented on lockflow about it). I doubt he's lobotomised either.
I-Shoji, it's possible to make space to get the leg in quite easily most of the time. Even if you do stack and try bring their head to their knee, assuming they are as flexible as myself, they can simply let you and turn their hips and still score the turnover. Or another option isd to simply anklepick the person stacking you, they fall back, you have a leg trapped.