22.5 wsm question

I have not done it, but did read on another site that is works pretty well for smaller/shorter cooking.

I am sure you'll need to experiment a bit to figure out how it works in your cooker to learn it's temp and cook time on a consistent basis.

I do.

I made a ring out of expanded metal the same diameter as the 18" WSM. It is more than big enough for any cook I'll do. It just sits inside the stock ring.
I also made a smaller ring for my 18" bullet for stuff like sausage ABT's etc. I'm more of a Turbo cooker than low n' slow so they work well for my style.

I always do it. I still can get well over 8 hours using the smaller ring.