Grace System is a Perfect Clear opener where the T-Block is held througthout the first bag and the other 6 pieces form a 6 × 4 rectangle. There is an 88.6% chance to achieve a Perfect Clear with the next 4 pieces.
Comparison to the Standard PC Opener[]
Placing the first T vertically will result in the same stack as in the Standard PC Opener (where the whole first bag was placed on one side).
In this case, there is still a 61.2% chance to achieve a Perfect Clear.
Refer to this link for the solutions.
If the T-Block is held throughout the first bag in Grace System, then the chance is actually higher than if the I-Block is held throughout the first bag in the Standard PC Opener. It is 88.6% for Grace System compared to 84.6% for the Standard PC Opener. Additionally, the solutions for Grace System are usually easier to spot. On the other side, the Standard PC Opener is more often applicable (it will always work, if you place all 7 pieces).
