Scratch building a scale model. Need to construct a motor box. Can you suggest the construction of a simple, yet strong motor box for a 3 cylinder radial. Thanks. Chic

Hard to answer not knowing the exact airframe or size, some I've built just have the firewall glued to the fuse sides, no box at all

but I suggest you browse similar plans on Outerzone and you'll see how designers sometimes build internal box structures.