Programatically installing a UNIDRV User Interface Plug-In

I'm installing a UNIDRV based print driver using the AddPrinterDriverEx API
(not the INF file method) from a custom installation application. I need to
install a custom UI dll with it, but there doesn't seem to be any
correlation between the programmatic API and the OEMConfigFile option in the
[OEMFiles] INF install section.

I've tried putting my ui dll in the list of Dependent Files. Doing this
makes it install with other files (the GPD etc), but UNIDRV doesn't know it
needs to talk to it via DllGetClassObject

Any help would result in much rejoicing on my part...