[NoCmpromiz]

We simply cut out the screen,

Just an additional thought.. Depending on the type of flue cap you have, you might need to keep in mind that a screen spark arrestor also serves to keep critters (squirrels and sparrows come to mind) from taking up residence inside your chimney during that part of the year when you aren't blowing smoke up it...

So you might need to replace the screen with a suitable critter stopper ;-)

[Cicero]

So far so good.

But I probably should have been even more specific. It was a tin sheet with holes cut in it. We removed that and put in a wire mesh fence instead, which lets a lot more air through.

That, and the metal roof!