Merciless Throatstanding Countdown

Now I want to test out this slaves stamina when it comes to throatstanding. Im not wearing any boots - I want to feel his mouth under my foot feet! I step on his mouth with my full weight and start counting backwards slowly - then give him a short break and step right back on again - and start counting down from a higher number! And again! And again! I want to test out his limits and push his limits - and he surely did suffer!