what are the downsides to adding a rear vent slider mod to a MB Gravitry?

[Bigheaded]

Both LSSMods & Klote make rear vent damper mods for Masterbuilts. Klote's one claims up to 4 hours more burn time from a full hopper of charcoal, which is a huge difference from stock. Even if it's just 2 hours under normal conditions that could add up quick if you smoke a lot. I made a pork butt yesterday and used at least a 15lb bag, maybe more as I didn't pay attention to how much was in it before I started. So it will help hold temp better (don't have a problem there) and Klote says keep more smoke in. So it seems like I could use less wood chunks and still get the same results.

I use mine a decent amount and plan to start using it a lot more, seems like for charcoal saving alone it would be worth it, but I'm trying to figure out what possible downsides there might be to this mod. If it's as good as it sounds it seems MB would have some sort of slide bar like the Chargriller one has.

 

[Chasdev]

Don't know if there is a downside but the designers know/knew the airflow into the firebox and probably made the exhaust in some relationship to that air flow.
How will pressurizing the cook chamber lessen fuel consumption, other than making it run hotter which will cause the controller to shut off the fan at the set point?
I've got a 560 and if that gizmo works, I want to know too!

 

[Bigheaded]

Don't know if there is a downside but the designers know/knew the airflow into the firebox and probably made the exhaust in some relationship to that air flow.
How will pressurizing the cook chamber lessen fuel consumption, other than making it run hotter which will cause the controller to shut off the fan at the set point?
I've got a 560 and if that gizmo works, I want to know too!

Well I'm no engineer, and on top of that, I went to Southern California public schools. But my theory is seeing how big the vent is I'd imagine a good amount of heat would escape. Which would cause it to need to burn more charcoal to hold the temp. The Chargriller 980 has a slide to open or close the vent, so maybe there is something to it. Of course, if it was really as simple as that there wouldn't be a vent there in the 1st place. I'm guessing again, but maybe it's good to let some of the smoke out or you'd get food that was way too smokey. But that's just my Cali public school at work (or not working lol) I am sure somebody here would be able to explain the pros and cons. As of right now I'm liking the sound of 4 extra hours, I think I got about 10 hours out of a full hopper of briquettes yesterday on a 225-250f smoke.

 

[Chasdev]

Or it could be that they left room for "improvements" that will appear on the "upgraded" model.
Hey, I'm fine with that, I've already gotten my money out of mine and when it wears down to a nub, I'll buy another as the size meets my needs exactly.
I look at pictures of new smokers all the time and while I would love to have a great big fancy rig, the 560 fits in the space I have and holds way more meat than two people can eat even with vac sealing and freezing.