×I am not seeing how to use the lowest and uppermost west hallways to best get babies into the the middle corridor so that tar can activate the 1x1 plates in there.

×betthro uses north passage first

×I can get a lot of tar babies, but then they'll hold down the plate and I can't move further on the south side.

I can get babies to hold down the plate at (14,16) while tar grows, but by the time the tar grows I can't go further west than column 14 so I can't get the babies out of the way.

So how do I block growth on both sides?

×Betthro uses north passage to get tar babies to activate the 1 time pp.

×Beethro uses south passage to get a baby into the south nook of the middle passage.

×Beethro waits while tar grows west in the southern 2 rows of the middle passage and babies form in the top row.
This can be set up relatively easily by simply stepping on the northern trap door of the middle passage earlier.