Http Get - UserFieldChar

I am trying to pull an event’s itemB’s userChar fields using Rest and note that the uri below only presents the API with the basic/ standard information set in the connected items.

http://<Server>:<Port>/assystREST/v2/events/10183439?fields=affectedUser[],itemA[],itemB[]

I have tried explicitly calling the field in the web request uri with no luck.

?fields=affectedUser[],itemA[],itemB[userFieldChar12]

This information appears if we run a second pull using the item id extracted from the event, but that seems a bit wasteful and we are able to pass it in from the AP as a parameter if necessary. But I was wondering if anyone was already doing this and whether you might be able to give me some pointers?

Thanks in advance.