I just recently discovered a new way of achieving a Mechanical T Spin Double loop in Tetris. So far I have 4 videos which showcase how this can be achieved. In fact copying the videos exactly is the most reliable way to do it. It requires some luck as to what blocks come before other but if you get past the beginning stages it is transformed into the Mechanical TSD except with no gaps and a longer back to back chain scoring more points and sending more garbage than even a traditional Mech TSD. Additionally, not one single T piece is wasted. Each one is used to score a T Spin Double and it’s possible to even get 40 lines using only T Spin Doubles if you really try hard.
It is based on the reliable TSD opener but the fact that it takes certain block order to work makes it actually unreliable in vs mode. But in single player modes you can just keep restarting until you luck out.