@buttman What is the date of your Blue 18? Not that is matters now you found out the hard way as well.
I found that out when I modified my 18" Red "G-Spot". I swapped out the ash can assembly off an 18" OTG. And I believe it was
@Troy that mentioned that the one-touch vents were larger on the oldies.
Also what I found on the 18's was the leg socket orientation is off somewhat - (unlike the older 22's) and I was able to trim a little off the ring tab to make it a clean solid fit without drilling and using self tapping screws or the hose clamps.
At first I was a little peeved buy the gap and stuck some high temp 3M duct tape over it, but I usually empty the ash before each cook and its never been a problem for me.
Since I took pics of the mod, I added Cajun Bandit legs and found a drum barrel lid for it to cook over as all my other cookers I use galvanized drip pans from NAPA when cooking on the wood deck.