I am mounting my DA 50 to my Extra 300LX. What's the best way to get the engine centered in the cowl. I know on the 540 Edge the cut out for the engine made it real easy. This plane has that "big grin" opening and I don't want to muck it up.

I thought about measuring side to side in the opening and center the engine in the opening but it just doesn't look right that way.

Also where does the top of the spinner back plate line up in relation to the cowl top?