Yeah, I was being 100% serious as that is the only way know of, other than 3d printing, to make these ships. And it seemed the only issue you had with FW was the material and not the sculpt, so making casts seemed like the solution. On top of that you were rather vague in what your "workshop" was. Sorry if my answer seemed terse or brief, but I was in my phone.
If you are looking for instructions on how to cast, well that wasn't clear in your first post, and I wouldn't be able to help. A Google search though can easily reveal a ton of helpful how to's.
I too have no idea what IGS stands for.
