Underfoot, spell ids under a 32767 seems to be fine as this is what I had to do to get the other custom spells I've created so far to work correctly.
You were part of that discussion actually:
http://www.eqemulator.org/forums/sho...49&postcount=9
There's a big blank void in the 28000 range so that's where I've been putting my custom spells.