index generation for HTMLHelp using DocBook XSL?

I'm using a DocBook customization layer and generating HTMLHelp in 
Arbortext 5.2 via File... Compose... For HTMLHelp...

I specify which XSL to use, and get a .chm file, but the index tab isn't 
there! In the XSL, I have specified:
 <xsl:param name="generate.index" select="1" />
 <xsl:param name="htmlhelp.use.hhk" select="1" />

I've also tried setting htmlhelp.use.hhk to 0, but I still don't get an 
index.

If I change over to using the .style file, the index will generate! 
However, I lose some of my control
over the processing this way. I'd really like to use the DocBook 
customization layer.

Any ideas how I can get the index to generate?

Thanks and best regards,

--Scott