custom Javascript issues after upgrading from 5.3 to 6.0

I've currently upgraded from Arbortext version 5.3 to Arbortext 6.0 M100 and I'm having some problems with porting over our custom javascript/ACL.

One of these customizations is a simple function run when the document is first loaded that checks a couple attributes of the root note:

var actDoc = Application.activeDocument;

var docRoot = actDoc.getDocumentElement();

var rootName = " + docRoot.getTagName();

Right now, docRoot is returning null which breaks the getTagName() call. Other exceptions in some of our other custom ACL also say:

Wrapped com.arbortext.epic.AclException: [A12653] The "detail" command is illegal for a text file.

All our custom code is running on 5.3 without hiccup. Are there any caveats/details I need to know about with custom javascript/ACL when upgrading from such an old version? I know Arbortext 5.3 used Rhino as a Javascript interpreter, did anything change there in the updaets maybe? I'm really lost here and would appreciate any input.