(1)  After initial vowels
     for the second letter:           b  d  l-m  n  p  r  s-t  u-y
     use number:                      2  3   4   5  6  7   8    9

(2)  After initial letter S
     for the second letter:           a  ch  e  h-i  m-p   t   u
     use number:                      2   3  4   5    6   7-8  9

(3)  After initial letters Qu
     for the second letter:           a  e  i  o  r  y
     use number:                      3  4  5  6  7  9
     For initial letters Qa-Qt, use:  2-29

(4)  After other initial consonants
     for the second letter:           a  e  i  o  r  u  y
     use number:                      3  4  5  6  7  8  9

(5)  For expansion
     for the letter:              a-d  e-h  i-l  m  n-q  r-t  u-w  x-z
     use number:                   2    3    4   5   6    7    8    9