Both of mine are welded in. Never had a need to get below the RF baffle to do any cleaning, but I suppose you wouldn't have to weld it in if you were able to get a good seal all the way around.
Team: Smitty's Real Pit BBQ
Superior SS-3 - Courtesy of Gainesville Jaycees and Superior Smokers
2 Custom Built Reverse Flow Stickburners
Weber 22.5" WSM
Weber 26.75" OTG
Weber Blue 2000 Stainless Performer