Due to it's lack of flexibility is there not a serious danger of the fibreglass cracking and the water getting underneath ?
They make boats out if fibreglass don't they?
My first and 3rd vans were fibreglassed.
I loved it!
Only negative: it looks the daddy when first done but after a few months if chucking a pressure washer in, bucket sliding about a bit etc it gets scratched.
And it'll never (IMO) be completely water tight cause at the back of the van the water creeps in there.