I never shoot for any weight when I build. I just build the kit then grab the hole saws and drill bits then remove anything that isn't in A stress area. The wing is not stiff enough for racing out at the ends so I put in the shear webs all the way out then removed the centers. I have them set up like I-Beams. It worked and the wing is stiff now. There is A lot of area in the fuse that can go too.. I did the same thing to the Kaviler I built for that class. You don't need all that heavy sheeting on the wing and fuse sides.
All these planes are built for is racing, go fast and turn left is all they do so the stress areas are easy to find and stay away from. I also use A lot of my own contest grade wood, much lighter.
Sig makes A great kit but there wood selection leans to the heavy side and the design is made very stout. They can take A heavy hit, mine can't.