Here's a link to another site that gives details on how to line up hole.
https://johnsgardenjournal.wordpress.com/2011/01/12/adding-offset-fire-box-vertical-smoker/
It looks like the char-griller is the only viable option for a bolt-on mod these days. Brinkman went out of business late last year, so that changes things. I just added some supports to my legs to stiffen up the whole shebang. Now I can move it as one unit without it flexing. I used some support brackets from server racks. Drilled and bolted them to the legs. Made a couple of bends for the angles, used sae 1/4-20 bolts, stainless of course. I may tack weld the corners of the firebox to the smoker box for added support. If I get 4 or 5 years out of this, I should be happy. Gonna keep it covered as rust never sleeps, especially so close to the ocean ! Yikes.
Outside is treated with a rust inhibitor/converter as any rust appears. For inside grates, etc - I just keep treating with canola oil till they season. I found when I burn with wood, charcoal AND lp, it goes to around 450 for a good cleaning. Just lp, firebox vents shutdown, will run at a stead 275 degrees (14000 btu burner). That's too hot for the long slow smoke.
So I use the firebox for the main cooking, slow and low at around 200 steady. I cover the bottom burner hole, to control ventilation from firebox (intake) to output at top of smoker (vent control here too).
All you need to do after the wood and charcoal simmer down to a steady burn is keep plenty of bbq sauce, wood, and beer on hand.
Tune in a baseball game and enjoy the day. Feed a chunk of wood or charcoal every now and then. Do NOT throw in the meat till you have a good burn going (be patient - that's what this is all about).
I already ruined my first chicken using a beer-can cooker. Temp was too low and it got more soot than anything (creosote). You can get a good smokey flavor by mostly cooking covered in foil, bump up the temp with fresh wood towards the end, then uncover for 30-40 minutes for the final smoke. I do 200 degrees for the duration, then 250 for the last 1/2 hour. That seems to work really well, without having to worry too much about how much smoke. And for the last 1/2 hour is when I add the apple juice soaked hickory chips.
Imparts a good flavor. I'll be trying the jack daniels' oak chips this weekend on some beef.
UPDATE: Just added 1/8" steel plate to inside lower bottom to help support and mitigate the heating of the thin metal backside of the smoker. Here's the pics of the plate in place. Used a plasma cutter to cut the hole and drilled the holes using a drill press. I actually was able to get all 8 holes lined up first shot! Burning off the new metal now.