Yes, it seems like they are compensating the FB being too small by making the throat too large. That's part of what makes the store bought units so hard to get them dialed in, not to mention the thin material that they're built from.
breavis wrote:One question about firebox size-I see where it's not recommended to make the firebox over 115% but what percent would be minimum I.e. 95%?
Generally 110% is the target. Just guessing, 100% is probably as small as I would ideally go.
The intakes can be larger than recommended because you can close them down to the required size for your desired cooking temperature. As for the exhaust, I like to keep it as close to 100% as possible but I like for it to be tall enough to keep the smoke out of my eyes so I might have to add a little length to the stack. I also have a damper on top of my exhaust so I can close it down a little bit if needed.