Hi,
Well worth some of you time reading our
Builders Guide and
Buyers Guides for starters. Also we have interactive design guides for various systems in a hovercraft
HEREI would gently suggest that most your design experience is probably not directly transferable to hovercraft (apart from some of engine/transmission bits) - hovercraft are a combination of aircraft design technology with pneumatics thrown in for extra interest! The lightest (VERY important for hovercraft) and strongest craft are made using lightweight composite core hulls - it weighs around half the cold store type panels you mention and uses structural core foam rather than insulation grade,
In the 20 years I've been involved in hovercraft I've yet to see a successful (as in does something useful) self-designed craft - the odds are against you but please feel free to surprise me! If you need any help let me know.
Electric craft have been the subject of much interest on here (a quick search will show up the results) but no-one as yet has overcome the obvious limitations of electric.
Cheers