Well after reading that, I guess it is optional, it does say at the top, accepted at the AGM.

I still say 4mm for the deck, but if you've your heart set on it, not much I can say, accept, that adding extra material to beef it up and having two layers of glass, would probably weigh more than having the 4mm with one layer of 100g/m cloth.

Good Luck though, its all good fun.

Regards