MCD Spin

MCD Spin, invented by MaëlMCD. This sends four T-Spin Doubles and guarantees a nice following 3-6 stacking or LST 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, to continue with the MCD Spin, the S piece should be put on top of the first bag's J piece, but it is recommended to simply go for regular freestyle stacking. 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.

Alternative

If the opener is attempted because of early S, but can't be fully done on the right because the queue doesn't allow it, the four T-Spins are still possible, although freestyling will be needed in order to do it. Here are a few examples :