Problems with Tuck Ups (MN/PE1)

Hello!

I have this problem regarding Tuck Up Training. When I reach the highest point, I try to balance on my tailbone or slightly above, but it hurts my tailbone when I do so. This results in me rolling to the left side and balancing slightly left from my tailbone (on the upper end of my left glute).

 

How could I fix this to not develop further imbalances?

 

Also, I recently noticed some lower back pain on my right side arising, could this stem from this unsymmetrical exercise?

I had an operation for a pilonudal cyst a few years back and the yoga mat makes a HUGE difference. 

Thanks for the answers!

I'm already using a yoga mat, but apparently it is too thin still. I'll just add some more layers and hope this solves the problem!