I cut right on the gray/black line on the bottom. Resembles a bit of a triangle if you know what I mean. Here is anothertrick. If you mount it like I did about 10-20 degrees off center (inverted), then your glow plug will be hiding behind the cowl and you cannot get to it. Option "A" is on board glow which I did. Even though I have a big opening in the bottom, to make it wide enough to get at the plug would darn near cut off the whole bottom of the cowl.

So I had my self proclaim very smart boy in his 3rd year as a mech eng student build me a special tool. I took a regular small socket the size to fit the plug. then took a piece ot thin steel the size and shape of a hacksaw blade. I then had him grind down a pit of the socket leaving just enough to fit over the plug, then he welded the steel to the socket. Works great. I just slide it in the cowl and place it on the plug and turn it a couple times to get it loose.

I need to find my camera.