Ultralight wing board glassing schedule?

[Dontsink]

Would a full "Blue Foam" XPS  core board come out too heavy?.
The foam i can get is 32kg/m3 = 2lb/ft3
The advantages would be waterproofness and higher ding resistance/rigidity ,maybe allowing for a light layup of innegra and carbon.I would vacuum bag the whole mess.

In an 80 liter board a 2lb core is 2.5kg total.A 1 lb core would be 1.25kg saving.

Another goofball idea i have is to do some kind of "hollow" in the nose area, i think Salomon did some semihollow core surfboards back in the day "S-core" or something like that.
With XPS panels the hollow areas could be cut easily before gluing them up, not sure if the vacuum would just implode the monster

I often chamber/ hollow out my 2-2.5 lb EPS using a hot wire gouge. First I cut the board, with a hot wire, into 3 longitudinal sections. Left, right , center.  I do not chamber under or over track box or standing/kneeling areas.  The chambers always leave 1-1.5" of foam between it and the outer surface. each chamber is 2-4" wide with 1.5" solid walls in between.  Two forward vents are used but the gas pathway is from one vent, down length of Left side of board to tail, across to right side of board at tail, back up forward to to vent on right side.  This is so if I do get a leak I can dry it out by just infusing air with an aquarium pump.  In essence, all chambers have one communication hole between them and the next chamber.  I vacuum bag using very low pressures(4-7 inH20(? units).

Great info,thx Peter.