The front edge of my firewall is 2 inches from the forward bottom area of the windshield. If you cut your front off, allow the sides of the fuselage to extend 1/2 to 3/4 inch past the firewall to allow for triangular stock reinforcement. Follow the previous angle of the firewall (slightly slanted) and it will also have to be cut from larger stock. Going back to the engine, mine is a smooth running as any glow engine of similar size.