I read vargsvans’ great post shortly after I started my WK journey, and I found as I progressed that like them I was having increasing trouble with some of the kanji mnemonics, especially in distinguishing between long and short vowels, so I took vargsvans’ suggestion and read Moonwalking with Einstein.
Armed with the information I learned from that book, I am now in the process of reworking the mnemonics to better suit the way my mind works (I really like consistancy, I really don’t do well with gross humour/violence), with a focus on the onyomi [edit: 1 & 2 mora readings] since most of the main readings for the kanji are onyomi, and to that end I asked rfindley to crunch the data for me, which they kindly did with alacrity!
So, in case anyone else is interested in how often they will need to remember particular kana/mora/syllables/sounds, I’ve made a chart. I was interested to find that the combos (with little や、ゆ、よ）only occur singly / in first position, never in second…
For simplicity, if a mora didn’t show up at all, I removed it (the whole ぱ line is gone) and I didn’t bother entering any zeros.