have you tried using a firering from a 18" WSM? I've heard this helps managing temps better in the 22.5" WSM's.
We use a 18" WSM at comps and it locks in at 230* for 8 hours and never wavers. We've never considered using an electric fan only because there's no need.
Mark - part of Cat Sass BBQ Team. Community Development VP - Secret Squirrel Society (but we don't exist)
Member: Mid Atlantic BBQ Association. Member: KCBS. CBJ # 31818
"Life's too short to drink cheap beer or eat crotchpot BBQ"
NB Bandera - refurbished; Two Big Green Eggs: Poncho - Large, and Lefty - Small; Weber Kettles; 6' fire pit; Super fast Blue Thermapen