Aitch Stacking

Aitch Stacking is a C-Spin opener. It is originally invented by Aitch himself in 2018, but later named by Agent 1568AH in October 2021. Originally, the first bag was stacked with the J piece notch being made first, and therefore the overhang being J or IL from the second bag, but because of stacking problems, the first J piece makes the overhang first, and therefore, the second J piece will make the notch.

First Bag
If the I piece comes early (not necessarily being the first piece), almost all bags will work, but if the I piece comes as the first piece, it is always possible to assemble this opener, but the TKI 3 Opening would be a better choice because one can make a T-Spin Double in one bag.

When Aitch first made this opener, the first J piece is placed where the notch would be made. However, because of stacking problems, Agent 1568AH changed the placement of the first J piece by placing it on the overhang first. So, if you can stack the former, stacking the second bag would be easier; otherwise, stack the latter.

The overall setup rate when the J piece was made as the overhang and also counting its mirrored opener, is 75%. If the J piece was made as the notch first and also counting its mirrored opener, the setup rate is 68.57%. The mirrored openers are not shown for simplicity.

Second and Third Bag
All stacks here will be shown if the first bag was stacked with the J piece being the overhang.

Perfect Clear
Ideally, you should be able to stack one of these setups for a chance of getting a Perfect Clear in the third bag.

Standard setups
These setups were chosen by Agent 1568AH and he also discovered setup F.


 * Setup A (48.33% setup rate, 96.90% PC rate, 12 minimal solutions): This is the most ideal way to stack the second bag for a chance of getting a Perfect Clear in the third bag. Furthermore, one can use an S-Spin to place the S piece, if the O, L and Z pieces were already placed.


 * Setup B (66.67% setup rate, 95.79% PC rate, 32 minimal solutions)


 * Setup C (24.44% setup rate, 93.02% PC rate, 10 minimal solutions)


 * Setup D (41.11% setup rate, 91.19% PC rate, 7 minimal solutions)


 * Setup E (70% setup rate, 91.03% PC rate, 20 minimal solutions)


 * Setup F (52.86% setup rate, 85.28% PC rate, 10 minimal solutions)


 * Setup G (40.63% setup rate, 80% PC rate, 8 minimal solutions)


 * Setup H (36.51% setup rate, 79.96% PC rate, 9 minimal solutions)


 * Setup I (45.56% setup rate, 62.34% PC rate, 4 solutions): Normally, setup F should be used intead of this, but for some cases this must be used instead of the former.


 * Setup J (66.67% setup rate, 40% PC rate, 3 solutions)

Supplemental setups

 * Setup 1 (23.81% setup rate, 97.98% PC rate, 53 minimal solutions): If the I piece come before Z also hold the O piece at the same time, the most ideal setup can be stacked. If you must place the O piece, it should be placed on the overhang (setup B).


 * Setup 2 (21.43% setup rate, 97.42% PC rate, 23 minimal solutions): If you must place the Z piece, you should be able to assemble setup A or G.


 * Setup 3 (24.76% setup rate, 96.07% PC rate, 46 minimal solutions): If you must place the O piece, use setup E.


 * Setup 4 (1.90% setup rate, 94.74% PC rate, 32 minimal solutions): It is not possible to score a T-Spin Triple and get the shape shown in the second diagram. On the other hand, there is a chance to get a Perfect Clear after 6 or 8 lines. In this case, after the T-Spin Double, place the Z, then S, and then L to clear a line.

Compromise
If it is impossible to stack any of the Perfect Clear setups above, you can always stack one of the two ways below, depending on the order of the L and O pieces. A T-Spin Triple Tower can be stacked after the T-Spin Triple in either case.