Check credit unions. I got about 3% on my rig back in 2011, and credit has only gotten easier to get since then.
I personally like going the pre-qualifying route. I also made sure I had 20% cash on hand for a down payment, so I'd not be upside-down if something happened and I would have had to get rid of my rig in an emergency.
What about looking at used rigs? Sometimes a used TT that has no water damage might be just as good, and you are not taking the depreciation hit the second you sign the PDI form.