AB40k Maintainers

I'm sure this has already been answered but I've just recently gotten Army Builder and was looking to see how to add a Tervigon as a troop choice. I appear to have the prerequisite amount of Termaguants but don't see an option to add the Tervigon. Is not possible or been FAQ'd out of existence since the codex came out? I thought it might have something to do with how things are internally done but it appears the Blood Angels Death Company Dreadnaught appears to work / validate correctly when there isn't enough Death Company models selected. Is it something to do with a "double" entry (i.e. Tervigon as a HQ and a troop choice)?

Add the Termagants, add the Tervigon. Select the Tervigon and scroll to the bottom. There is an option to change it to Troops. Oh, and you have to dial the correct size on the Termagants.

Homer