[TCArknight]

Thanks Mathias!

I found the issue. the setchosen[] process apparently requires a trusted script. This is my final script in case anyone else wants to do similar...

    <!-- If the ability needs a specific selection, set it based on the Target1.? tags -->
    <eval index="4" phase="Final" priority="1000"><![CDATA[
	  trustme
	  
	  ~ done if this doesn't have a Target1 tag
	  doneif (tagcount[Target1.?] <> 1)
	  
	  ~ if we do have a single Target1 tag, we need to set the usrChosen1 to the target
	  var myRef as string
	  var tagexpr as string
	  
	  myRef = tagids[Target1.?,"|"]
          myRef = replace(myRef,"Target1","Reference1",0)
	  perform this.field[usrChosen1].setchosen[Ability,myRef,hero]
	  
      ]]></eval>