I would check with someone who has knowledge on trying times. Wood chip and clay at this time of the year may be pushing it. You don't want the mix to freeze. You may drive the moisture out from the inside with wood heat. It is the outer layer that may be susceptible to freezing, and a render on that side would delay drying even more. If we should settle into a wet fall your drying times will be longer than the 6weeks and that puts you into November or more.

I am saving all the chips from my boring machines, nice half round chips.