Oh yes
I would recommend it. I would say that on an item that large, 3/8 to 1/2 inch thinckness silicone (in layers of course), and a rigid fiberglass jacket. Depending on the shape, you may have to make your jacket in sections (maybe even your silicone) to avoid mold lock around your undercuts.
For instance, in the pic below I see it being at least a 2 part mold.

FP