The point of fibreglass box is to ensure any leakage cannot build up inside vehicle leading to asphyxiation or explosion. No ignition source= no bang. Containing an explosion would be akin to squezing ones cheeks against a dose of Bali belly. Destined with failure. Kevlar bags probably best option. Removing likelihood of reaching combustible air/ fuel ratio via ventilated box and preventing ignition source is quite workable. The weak link being operator error of internal appliances.