In the CUIx, try NOT specifying a path at all, just use the help file's name. In your .bundle's PackageContents.xml file, specify the .bundle's relative path as part of your SupportPath XmlAttribute instead. This *should* add the appropriate SupportPath to SFSP, which allows the help file to be 'found' for you at runtime; example:
Code:
<!-- snip -->
<Components>
<RuntimeRequirements OS="Win32|Win64" Platform="AutoCAD*" SeriesMax="R20.1" SeriesMin="R20.0" SupportPath="./Contents/MyHelpFileFolder" />
<!-- ComponentEntryHere -->
</Components>
<!-- snip -->
HTH