Help with Screech / Overwrite Method

[Bohbo]

I am trying to make a series of spells lets say 3.

Stance 1
Stance 2
Stance 3

For casters.

I had this working and somehow its broken now and I have spent a few hours banging my head against spell stacking.

I originally used screech with two -1 values using AC value of 1. This worked and allowed spell to overwrite each other but only allow 1 up at a time.

I CANNOT get any form of spell overwriting / stacking to work.

Currently I am using Slot 11 and Slot 12 to do the following

Slot 11 = 216 accuracy with a primary value of 1 Slot 12 = Screech (123) with primary value of -216.

Problem is both spells seem to cast and go on at once. I tried making one +216 also but it didn't seem to make any difference.

If anyone can guide me in the right direction I am incredibly frustrated with this problem.

Also I tried SE Stacking Overwrite of 149 in slot 12 on as value 1 = 216 and max value = 1 (also tried 2) neither seemed to work.