Why not seat the 1/4" balsa IN the brass/aluminum angle stock then shave/sand off the excess? Go slow, use a SHARP blade and pay attention to grain run-out so your blade doesn't 'lift' a chunk of wood. YES, 1/2 of the balsa is going to be WASTE but, that's the price we pay for having fun. Usually, hand/tool pressure is all that is needed to keep the balsa seated in the metal. If you need long lengths, work up something to support the whole thing.
Dave A.
Key West, FL