I'm having some trouble getting calls forwarded to a voicemail box after a ring no answer on a hunt list.
I've tried configuring another line group that has an extension with forward all to voicemail set.
I've also tried setting the hunt forward settings on the hunt pilot to the voicemail box - that didn't work either. I was able to hit Unity, but it didn't go to the mailbox. It went to the General Unity message.
I'm using Callmanager 4.2.3sr1 and Unity Connection 1.2.1
Your method using the Call Forward settings on the Hunt Pilot is the way to go. Check the Directory Number you are using for this mailbox (should be the Hunt Pilot #)
Sounds like you are halfway there :)
Hope this helps! Good luck.