Sandwich/gelocat panels construction

Hi guys, im planning on building a larger model which is around 4m, and want to use sandwich panels with gelcoat skin in 36mm size.
Altough its alot more rigid than building in plywood, i assume i need some sort of safety cage to stiffen the entire rig properly on the chassis, but question is, how much and how strong do i need to build it?
Can i integrate alu bars in the sandwich panels, or do the panels have to be attach to a cage that is hard mounted to the chassis?
Anyone else here built their camper in sandwich panels that might share their experience on this?
Cheers
Altough its alot more rigid than building in plywood, i assume i need some sort of safety cage to stiffen the entire rig properly on the chassis, but question is, how much and how strong do i need to build it?
Can i integrate alu bars in the sandwich panels, or do the panels have to be attach to a cage that is hard mounted to the chassis?
Anyone else here built their camper in sandwich panels that might share their experience on this?
Cheers
