Carbon Fibre Mold

Hi All

I am trying make a carbon fibre negative mold of a complex part I have made for a drone. The part has taken hours if not days to sculpt on Shapr. What I am trying to do effectively is create a carbon fibre “exo skeleton” Shell of the part that I have designed that will be 3D printed in nylon and become the core inside the shell. The shell itself will be exactly the same shape as the printed core, but will have a wall thickness of 1mm so the negative mold features will need to be 1mm larger than the actual part I’m printing . I want to avoid going down the lines doing the same design but a 2nd time but larger, because it took a long time. I have tried the shell command which will make the outer dimensions 2mm larger, but once done I cannot then take 1mm from the internal dimensions, scaling will not work either because now all the features are in the wrong places. Please Help

Do you have a picture of the model? That will help to figure out how to go about it.