Pictures and mods
I built one of these back in the 80's. Well I built the one pictured below. I think it's the same as yours but I don't remember what my box looked like.
The one I built was actually designed for a 29 size engine as I recall. Or maybe it was for a 19. The wing was a flat bottom and tons of down thrust in the engine set up.
Well, I did just a couple mods. First and foremost, I made rib extensions (half ribs for the bottom) if you will. Pieces that I glued on to the bottom of the existing ribs to make a semi-symmetrical airfoil. And that wing came out thick at the root. Kind of an out of the box approach but it worked. Then of coarse the next thing was to get rid of all that down thrust and bolt a OS 45 FSR and eventually adding a pipe on it.
I loved that plane. It was pretty fast too. One day I was doing a spin and left it in a little too long.