I'm running the same GI as you, same gears. I'm 160 lbs, so that might help. I'm not great at skid stopping. Practice on dirt or gravel or a wet wooden bridge deck. You're using foot retention right? Because pulling up with the front foot is as important as pushing down with the back. Stand up and lean forward a bit. It's also a bit easier the faster you're going. I have a hard time holding a skid when I'm not going very fast...I'll skid a bit, then a half rotation of the pedals, then skid a bit more, etc. Or just use your brakes. I'll never remove my front brake because I still find it handy sometimes.