MCD Spin

MCD Spin, invented by MaëlMCD. This sends four T-Spin Doubles and guarantees a following nice 3-6 stacking.

The first bag is always stacked as shown below and has a 43.50% build chance (56.03% with mirrored).

Second bag

The second bag can be stacked different ways depending on the queue, though the general idea remains the same, stacking the I and S pieces to make the overhang for the incoming trinity, and taking the T-Spin with the T piece. Here are a couple of ways to stack :

Unfortunately, there is a 2.78% chance that it is impossible to build the second bag with the S piece on top of the I piece. In that case, the S piece should be put on top of the first bag's J piece. Here are all the cases where the S piece has to go on top of the first bag's J piece :

In these cases the T-Spin should be done before putting the S and I pieces, as if both are placed, there is no way to do the T-Spin.

Third bag and onwards

The third bag involves stacking pieces on the right while putting the S and I pieces here :

If the second bag's S piece was placed on top of the first bag's J piece, the third bag's S piece should then be placed as shown below.

Note that to complete the fourth T-Spin Double, the four minos highlighted below have to be filled, but if an O piece is used here before the second and third T-Spins, the Trinity/STSD will be inaccessible. Multiple ways of stacking on the left are shown below.

After the fourth T-Spin Double, continuing with 3-6 stacking is recommended. It is also possible to continue with 2-7, which allows for LST stacking or ST stacking.