It's certainly been done before. You ought to be able to find at least one discussion on this plane in the thread archives.

The standard tips for building light also apply. You can replace lite ply with balsa of the same thickness, aircraft ply with lite ply, slab surfaces with stick-built "truss" structures. On a solid plane like the Sig SE, you can probably save several ounces just in the stucture; it's overbuilt even for glow power.