By now, their vision is really good, you can definitely start to useblack ink instead of red ink, and gradually reduce the font size.
Now in terms of two letter words, I reprinted them and retired all the big 22" x 6" cards.
I reprinted them (Landscape) so that I can glue the "halved" A4/USLetter into 2 pieces, and then it fits perfectly on the 11" x 11"halved, when he was 6-9 months. Font type and size used was Arial 180
Now, at 14 months, I print four rows of words on a Landscape A4/USLetter and slice them, then glue to the 11" x 11" poster board.
Here is a copy of what I did, its couplets that are car related, interior and exterior. Font type and size used was Arial 72
学习了，感谢分享！