Re your armoured question, My race team linleyswangp.com using materials from a supplier who specialise in bulletproof kevlar. They have made various items for special forces and I have a hull we could lay up for you in this material.

Re tubes I would go for hard foam tubes overlayed in Hypalon. With inboard diesel engines and surface drives.

If you would like more info, please email myself at tom @linleyswangp.com

Kind Regards,
Tom Montgomery-Swan