> I still haven't got those damn aorist figured out yet...
I don't think you're alone. I find Szemerenyi's explanation for the long
vowel very odd. If the vowel length were simply from the insertion of -s-
after a resonant, we would expect Sanskrit stems in -i to produce a
long -i:s in the aorist, but they don't, they give us -ais- / -es. Likewise
stems in -u give -aus- /-os. (These of course are long and short a + i,
long and short a + u in Skt) Examples:
stem ni: = lead
aorist 4: anaisi:t, nesati
stem pru: = flow
aorist 4 prostha:s
stem stu = praise
aorist 4: astausi:t, stosat, etc.
This looks to me much more like the insertion of an -e- than compensatory
lengthening!
Peter