Tiny infinite growth patterns in Serizawa!

[137ben]

I know there is already a Serizawa thread, but I think this deserves a thread of its own. I was searching for 1d infinite growth patterns, and found the following:

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x = 22, y = 50, rule = serizawa
6.3BA2.A2B16$7.4A2BA13$6.2BA2.A2B9$A3.B.A7.2B4.AB11$5.B3.A2BA2.BAB.A!

This motivated me to search for smaller patterns, and eventually, I found a 1 by 4 pattern with infinite growth!

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x = 4, y = 1, rule = Serizawa
A2BA!

At this point, I did an exhaustive search, and found that no pattern in a 1 by 3 box exhibits infinite growth, and only one pattern in a 1 by 4 box does.

Following this, I did a complete search of the 2 by 3 box, and found that no 2 by 3 pattern exhibits infinite growth. Thus, the only bounding box left to check is the 3 by 3, at which point the bounding box question will be fully answered.
EDIT: knightlife has found infinite growth patterns in a 3 by 3 box, completing the question!

But, as I've said on (several) other threads, I find bounding box to be one of the less natural measurements of pattern size. In the way of minimum population, a 3 cell infinite growth pattern was found on the other thread:

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x = 3, y = 4, rule = Serizawa
.B3$B.B!

I did a complete search of 2-cell patterns, and none of them exhibit infinite growth, so that question is answered.

Another way of classifying pattern size is by using the minimum p such that the pattern is completely contained in a p-neighborhood (using the metric induced by the CA neighborhood). For the Moore neighborhood, this translates into bounding square, so I'll admit that for rules in the Moore neighborhood the bounding box has some merit.
For the JvN neighborhood, a radius 1 neighborhood would be the plus-pentomino. I did a complete search, and found no infinite growth patterns which fit in a plus. Since the 1 by 4 pattern fits in a radius 2 neighborhood, this establishes the minimum radius of a pattern with infinite growth.

Lastly, we have the bounding-polyomino. Any triomino fits inside a 2 by 3 box, so no pattern with a bounding triomino can exhibit infinite growth. And of course, the 1 by 4 pattern has a bounding polyomino of 4, so this is in fact the minimum.