I designed and built this model over 20 years ago. I designed it for a speed 400 motor and small NiCads.  Many years went by before I actually flew the model. After a season of speed 400 flights I switched over to a brush less motor and 3-cell 1320 size Lipo.  The model is a fast and smooth flier.  Weight was kept low by using 1/32” sheet balsa sides with balsa strips in the corners for added strength. The wing is built up with 1/32” ribs and open bay sheeting.