Sorry no definate answer here.

But when looking at the all up weight of the M20 of 120 kg (108 kg in the prototype versions) I would wager that the hull weight is close somewhere between 25 kg - 30 kg a piece. Otherwise I really can't understand that the whole platform comes out at 120 kg.

If it helps I give the weight distribution of another lightweight boat.

Hull 25 kg
beams (alu + stainless strap) 12 kg (M20 all carbon but also wider and if you run the numbers than 12 kg for M20 seems about right)
Mast + fittings (alu) 15.5 kg (I expect the M20 mast to be about 16-18 kg in carbon on what I know about carbon masts)
Mainsail 7.5 kg (will be about 10 kg for the M20)
Jib 1.5 kg
Spi gear + snuffer 5 kg
Boards 4 kg (M20 may be slightly lighter but not much as the boards are much longer as well)
rudders/stocks/tiller/extension 4.5 kg (These are carbon)
Extra like blocks lines etc about 7kg - 10 kg.

This boat comes out at 107 kg fully rigged with normal stainless steel rigging etc. In order for the M20 to come out at 120 kg (Texel rating measurements) it need to gain weight somewhere. As all fittings like stays etc are carbon or lightweigght spectra/dyneema line it must be found somewhere in the mast, hull, beams and boards. If we use the prototype min weight of 108 kg than the M20 must have 25 kg hulls, If we use the 120 kg as a reference the hull weight comes close to 30 kg.

That is the best I can do. And I replied because I don't think anybody but Marstrom himself can tell you the real hull weight.

I hope this helps you in any way

Wouter