Yeah it's 22mm inside, initially I only had one 15mm input and it just wasn't getting enough air into the smoker. Other people seem ok with 15mm but I think the 57cm WSM with all the vents sealed up with aluminium tape and a nomex gasket around the door and lid is pretty airtight and I need to be able to push more through.
I think it takes about 30 minutes to heat up when I remember to fill the water pan at the beginning, had a bit of a duh moment last time out with that one... I just got a bag of sandpit sand to replace the water on the next cook. When I didn't have the two 15mm inputs it seemed to take forever to heat up and struggled to maintain 120C even with the fan on full, that's why I changed to two inputs. Now it gets there fast enough and maintains it well at around 20% fan.

