Not sure where you are losing smoke, but here are some links and pics that I came across. The first one contains a number of pictures (not mine) showing how the SFB and chamber can be sealed. You can see how the main chamber is sealed. I've used a product made by Rutland, which is a flat rope-like material and glue it to the SFB openings with high temp silicone. viewtopic.php?f=2&t=15231&p=148348#p148348
Here are some pictures of my CG:
I've found sealing the SFB helps maintain temps better. The way the basket sits in the SFB allows air to flow through to keep the temps up. Additionally, I can pull the ash drawer out to help get temps up and close it when the temps are where I want them.
The rope sealer is attached to the SFB, not the drawer.
Here is a picture of the straps that I mounted in the SFB with screws. It sits just above the edge of the ash tray:
Here is another shot with the basket sitting on the straps: