Ok I was thinking the deck is very well fastened down so I might try cutting back the top 4mm sheet and then sanding through the adhesive until I hit the second 4mm sheet. Glass over the top of that with 2 layers of light cloth.
If I can shave a kilo then I might be able to reach min weight. Also I noticed a rule Proposal 6.5 to make the center beam optional. After reading the rules I am confused.
It states

(Accepted at Annual General Meeting, 3rd January 2007:)

Does this mean a proposal has been accepted to be further voted apon? or is the rule officially changed now?