here's one thing i do...using the main gear, i hang the fuse on a gate between my garage and patio...i secure the fuse with string to keep it from falling off the gate, and use a step stool for a work platform...the firewall is then horizontal, and it's much easier to align the engine, standoffs, and cowl...you can position the engine with standoffs to the exact location where your hub/cowl is centered, draw circles around the standoffs on the firewall, make an 'x' in the four circles, and drill...or use a template that comes with your engine...ken