What someone really needs to do is make a heavy duty weld on hinge with built in spring specifically for BBQ cooker doors. Have the hinge adjustable so you could use a wrench to load the spring to the desired pressure/weight of the door. Save having to add counter weights.
Looks great.
One question. Are you going to have enough ground clearance under the firebox ?
If you raise it up too much you the cooking chamber doors will be too high. You could make a locking latch like on my 250 gallon to help raise the smoker and still reach the door.
Looking Good That size smoker I would have gone with 7 - 8 inch stack you need to move a lot of air
Gary