Good and bad news,
Tobacco is bone dry ahead of schedule and I managed to cure some yellow, the bad news is the reason I know its bone dry is I almost burnt down the garage!
When I got the temperature to around 160F I could smell something strange when I walked into the garage, the material I made the inside of the chamber out of, a PVC sheet similar to what the inside of a fridge is made of although it stays stable up to approx 170F, it does get soft which wouldn't of been much of a problem except the glue I used to fix the sheet in place Liquid Nails doesn't do to well at high temperature, the walls and ceiling had started to fall off and warp as the Liquid nails had come away from the timber!
Moral of the story check that every material of your build can operate up to 170F at least, I thought that I had but forgot about the glue.
I think ill have to pull it all off and replace it with Fiber Cement board, Lots to learn with this Flue Curing business, Sadly I cannot at this time afford to buy the Fiber cement board (In New Zealand building materials must be a lot more expensive then in the USA, I got everything for free except my Thermostat, The MDF board that I used to back the PVC sheet, Fixing materials and silicone, That stuff alone cost me $150+ USD) so I guess I'm stuck with air or sun curing the rest of my leaf this season.