Yes that's how I tried first, assuming that unsupervised meant such. I also lengthen the transfer recall, but the call would return to voicemail. I didn't have any forwarding on the nite bell, so it took me some time to find which timer was the culprit. After reading the help on voicemail, it states that it's recall timer is 17 seconds when set to unsupervised.
If dialed direct, it worked as expected. Setting vm to supervised and increasing the recall timer to a value greater than the nite bell forward also seems to provide extra ring time. Since all my tests were dialed remotely, I only can assume the bell was ringing.
Thanks again,
John