There is a certain point in the modification process that you have to ask yourself if you wouldn't be better off getting a new smoker/grill or keep pouring money into a sub-par device that will really never be a great smoker.
For about a year and a half I owned the Char-Griller 5050 duo with the side fire box. In that time I made extensive modifications - effectively doubling the original cost of the entire unit! So about $350 original cost plus another $350 or so over the time I owned it. Did it work better? YES - it kept solid temps across the entire chamber and was effectively sealed against any smoke loss.
However - I think I would have been much better off in taking the $700 and getting a higher quality unit in the first place.
I ran into the same point under discussion in this thread - do I insulate the unit so I could smoke all winter or upgrade to a much better unit? After much research I purchased a Char-Griller Akorn Kamado style grill/smoker. I spent only $269 (Lowe's 10% discount) and it literally is 10 times the grill/smoker my last unit was. Totally sealed and insulated. Uses very little fuel. Produces BETTER results - tender, juicy meat - with much less work compared to the offset smoker. It is basically a poor man's Big Green Egg for 1/4th the cost yet gives you about 95% of the performance.
A side benefit is that I can sear steaks and make pizza at very high temps. It is rated up to 750 degrees F, but I have had it over 1000 degrees for short periods with no problems.
The only negative may be if you plan on cooking/smoking for large groups and you need a lot more space in your smoking chamber. Other than that I cannot see any negatives with this kamado grill/smoker.