I need to reiterate... OVERFLOW is not for flowing calls, it is for a recording, when a call is "in" Overflow it is still in the original ACD queue, it's the terminology that is messing with you. Overflow is just another recording point and should more appropriately be called Announcement #2! Calls are not flowing properly because the "device" you are using as the Overflow point is not a recording but being answered by a phone. Exactly what you are trying to due is not possible without using the Call Center application (a licensable server that manages ACD groups, even then I am not sure it would work exactly as you want). ACD in the 5000 is pretty simplified compared to other more ACD-centric phone systems.
You can easily route the call after a timer to a regular hunt group, you use it as the ACD groups RECALL point, when the recall timer expires the call is transferred to the Recall destination which can be a hunt group. So the call would sit in the queue until the recall timer expires, then it would be transferred to your hunt group and sit there until that recall timer expires than could be sent to an appropriate destination such as voicemail, auto attendant, or live attendant.
