I know door on 22 is bigger, and harder to seal due to that.
The stock door, is perfectly fine for the 18 imo.
Unless you step on it.
I bought CB door for 18, and sold it.
It didnt fit any better than stock . Maybe not as well. Bigger corner gaps. It didnt latch as well...lightly and tight.
It is so stiff, it flexes the wsm shell.
It ground porcelain off shell in bottom corners due to hardness/stiffness.
The z bend at bottom isnt sharp enough due to metal thickness.
It might have looked better...if your into that...thats all.
I think weber knew what they were doing with the door....at least on smaller wsms.
I think many have issues when shell is out of round......you can do that with a hit from fist....its that easy. That heavy stainless.door wont ever fit once that happens. Which is why people also buy gaskets.....