Hello everyone, I am looking for some help.
I want to take my Porsche car (987S), add some clay like material to the existing body and form widebody panels and then continue with mould preparation for carbon fiber. My question is: do you have any suggestions on what materials to use to add on the car in the first process of widebody positive moulding?

In design studios they build the car from brown/reddish clay. However, adding clay to the existing body may be a bad idea for many reasons, there is quite a lot of volume to add which translates into a lot of weight, it puts strain on the suspension and may just not stick. I am wondering what is the best technique, for example using some light wood ribs over the existing body, then filling the gaps between the ribs with foam and adding skin on top. But this would require a lot of time, and wouldn't be easily adjustable. I was thinking about creating volume from some hollow objects, for example scrunching some hydrophobic film (like paper) and adding plaster on top to create a shell of the desired shape.

But I really don't know what is the way to go and I would appreciate your input! Maybe you know of some lightweight materials that are good for this purpose?

Thanks!