For future thread readers:
The name to be used can be verified by right clicking on any API class node in the TOC and selecting 'Jump To Url...'
The text in the Current url that follows '/html/' is the necessary value.
Project Naming Method: MemberName
Code Class name: Finance.Invoice
TOC Url for the class: mk:@MSITStore:C:\Dev\APAR\Help\APAR_Reference.chm::/html/T_Finance_Invoice.htm
MAML code for an image hotspot link:
<image src="ObjectModel.gif" usemap="#ObjectModel">
<map id="ObjectModel" name="ObjectModel">
<area shape="rect" coords="0,0,100,100" href="T_Finance_Invoice.htm" />
Also note that using F5 to 'Preview Topic' for the aml page does not result in links that work.
You have to do a full build to test that validity of the links.