is it worth getting the fiberglass side panels or stick with the alluminium ones ?

The choice is yours!

I considered this, in the end stuck with ali because I reckoned that as it was easiest to attach the exhaust silencer to the side panel, ali could be reinforced and at worst would bend a bit, but fibreglass could crack-up and be alot harder to repair. As it happens with the reinforcement to the ali the silencer has hung from it fine with no movement!

I plan to make mine from Carbon Fibre.