Smoke stack mods

Vic, morning.... I'm not familiar with your smoker but I would keep the stack size the same and bring it down to about 1-1/2"s from the grill....  lowering the stack will keep the heat in the smoke chamber....  getting too close to the grill might reduce the air flow out the stack....   All mods are a trial and error project..  keep track of what you do and the smokers performance....  others are interested in your project also..... take plenty of pics....   Dave