Design of a Portable Cob Oven

I have been approached by Snow's Bend Farm to design and facilitate the construction of 2 identical and portable earthen/cob ovens. My friend Jeremy Crosby and I will be the two people facilitating the construction of this project together since we pretty much do all of our natural building projects together and we work very well together as a team. However, I am the one doing the design work for this and Margaret Ann Toohey and David Snow from Snow's Bend Farm have presented me with some very fun calculations. I will of course be getting a lot of critique and advice from Jeremy but the design work will be on my shoulders. Here are the requirements so far explained below.

I am limited to preferably no more than 1000 lbs and definitely no more than 1100 lbs since this is the lifting capacity of their tractor and that is how they plan to move these ovens around on their property.

The ovens will be on 2 separate 4ftx4ft wooden pallets with 2 sheets of metal over the top of the pallets to help distribute the weight and to hold in the insulation and concrete(both explained later).

The oven door will need to be able to fit a large turkey(height minimum) and a 12" cast iron skillet(width minimum). Since an oven door's height is 63% of the interior height of the oven and the height of the oven will be about 30" with the interior height being 24" this puts the height of the door at 15". If the width is 12" and the height can be 15" then I can place a half circle that has a diameter of 12" about 3" off of the floor. This gives room on the sides for easy acces for straight sided dishes.

They also want this to be roughly in the shape of the mounds that are located on the property. These mounds are roughly in the shape of an isosceles trapezoidal right prism. This part of the requirements are still a little bit fuzzy and I will clear this matter up pretty soon. Above is an image of an isosceles trapezoidal right prism to give you an idea what the shape could be.