I like very much the laying out of the acrostic letters in Psalm 9. The layout implies that daleth is verse 6. It is the ד that is missing - verse 6 (Hebrew verse 7) is ה.
There is a suggestion that Psalm 10 is also part of the acrostic, but there only one letter ל is noted. There are more: מ, נ, ס, ע, פ, צ are missing but the remainder ק ר ש ת are quite clear.
It is such a good idea to name and note the Hebrew letters. It gives the reader the sense that the text is old and different and not 'common'.
There are 8 opportunities to teach the letters, but they have taken only 2: Psalm 9 and Psalm 119. These are opportunities missed, I think. Particularly since all the acrostics in book 5 are perfect but each in book 1 is missing at least one letter.
My Sunday School children love learning the Hebrew letters. They particularly like puzzles - like why are the acrostics not perfect in book 1 but are in book 5?
These are ordinary uncommon children.