I have done it. I took plans for a .40 size pattern type plane and had a local blueprint company make a 66% full size copy of it and built a 2/3 size plane out of it. Powered it with an OS .15 FP. It flew quite well. It came out a little heavier than I had hoped though.
Really, you should change designs when you scale down, a scaled down D-tube wing with the same rib count as the larger prototype is needless overbuild for a 1/2A airplane. How often have you seen an 16-20 ounce 30-36 inch wingspan 1/2A plane fold its wings in flight from overload?