Its important to make sure your engine crankshaft exits the front of the cowling perfectly centered.

If the engine cylinder head will not fit inside the cowling without cutting a hole, then you should use the method bruce88123
has offered above.



If the the cowling will fit over the engine cylinder head, remove all items that will end up sticking out of the cowling, like the , muffler ,high speed needle ajustment screw,etc.
Then go ahead and mount it allowing proper spacing for your prop/spinner.

i like to clear plastic, like off a pastry container or any thin plastic. since You can see through it ,hole marking is very easy.

Once the cowling is mounted and all screw holes made,remove it again and , cut a piece of the plastic long enough to
reach from the needed cut outs back to the fuselage.
Tape the plastic to the fuselage and overlap your first cut out, such as for the glow plug. Once marked ,cut a hole large
enough for a glow driver.
Then mount the cowling laying the plastic strip over the outside of the cowling,and trace the hole you cut onto the cowling.
Do the same for high speed needle adjustment screw, muffler, etc. works great!