Dear Jim;

Thanks I will check out the Padamaalaa.

Sorry, I should have given an example of
changeable stem noun declensions. Here
is one from Collins (p 59):

raajaa - king

strong stem raajaan
middle stem raaju
weak stem ra~n~n or raajin

singular
nom raajaa (strong)
acc raajaana.m (strong)
instr ra~n~naa or raajinaa (weak)
dat ra~n~no (weak)
abl ra~n~naa or raajinaa (weak)
gen ra~n~no (weak)
loc raajini (weak)
voc raajaa (strong)

plural
nom raajaano (strong)
acc raajaano (strong)
instr raajuuhi (middle)
dat ra~n~na.m (weak)
abl raajuuhi (middle)
gen ra~n~na.m (weak)
loc raajuusu (middle)
voc raajaano (strong)

Note that Collins gives the Sanskrit versions
side by side and the stems used for each case
are almost the same. Perhaps Sanskrit grammar
has some answers.

Not quite clear whether all of these changeable
stem verbs follow the same patterns or
whether they are really all just unique exceptional cases.

With Metta,
Jon