Test 3 turned out to be a bit of a failure. It never really started smoking. Either the wood chips were too damp or it wasn't getting enough air. They started smoking as soon as I tipped them out.
For test 4, I dried some chips out in the oven and added a few more air holes to the cannister.
Test 4 seems to be going a lot better so far. Producing a light but steady steam of smoke at the moment. Decided to take advantage and try to smoke some cheddar. I did try to take a photo but the smoke wasn't really showing being very light.