I created a custom form region with the following message class:
"IPM.Contact.TestAddIn1.ClientRegion". I then created a new Folder within
the default Contacts folder to store these custom items. Finally, I created
a NavigationFolder within the Contacts navigation module which points to my
new Folder.

when I click the navigation pane folder it is raising the default Contacts
form, rather than my custom form. this is expected. the problem is that I
can't find a way to set my custom message class for this folder in order to
correct this problem. The DefaultMessageClass property of my folder is
read-only. Also when I first create my folder, the help file specifies that
the additional optional parameter should specify an olDefaultFolder type, so
I can't set it there either.

any help appreciated as Ive been stuck on this now for a while