I have been cooking on offsets forever. I have learned to cover them up with a shipping blanket, yup the kind you pack around furniture when you move. It holds the temp and it seals leaks. The blanket will turn brown first then after about 10 cooks will get nice and burnt but it will not catch fire. Give it a try by getting your off set to 225, then toss on the blanket, your temp will increase by 50 to 75 degrees in 5 to 10 min and it will stay there considerably longer than you have gotten it to in the past with out adding more fuel. You will go thru slightly less fuel and be able to control heat. People always get on us at competitions for putting our smoker to bed, but hey it works like a champ and it is the least expensive modification you can make.
Large Homemade Offset on a Trailer
Gentleman Jack and a $10.00 cigar