The scale factor in the cockpit area is one of the biggest issues. Compounding that, the German cockpits of that era were VERY tight even full scale. You might have to use a semi supine seating with much of your body forward like a modern sailplane with only your head in the canopy area. Engine nacelles are not going to scale well either, but for the opposite reason. These modern model based engines are going to be swimming in the scale nacelle OML. Long tailpipe too. But for certain, original drawings are going to be practically worthless for structural detail. Cardinal measurements are going to be the only use - it's an entirely new structure beyond that. You'd be better off starting with something like an RV for a sanity check on the structure. ...and to pile on a prior post, I can get you into an L-39 TODAY for less money than this project will cost.