I put everything together, and am having a few problems. I am using an MSR PocketRocket, but that shouldn't matter. My block parts and fin were made of brass, the screw was steel. The blocks were made it out of one piece of brass and drilled the holes before cutting it in half. The rod I put inside the brass tube was about 1.8 or 1.9 mm. There is a slight gap between the blocks (more so on the top). I was using Snow Peak canisters, and all of my testing was done in temps in the mid to low 20s (F). I did however, throw the canisters in the freezer to cool them and better simulate winter conditions before the testing began. Each test lasted about 10 minutes.
I cannot get the gas to vaporize properly. When the canister is upside down, I get a continuous fireball, even on very low power. Even after the stove heats up and the upright fin appears to be warm, but it does not appear to be vaporizing the gas.
To try to correct this, I added some thermal compound between the blocks and between the fin and one of the blocks in an effort to increase heat transfer. This did not work, and the stove never settled down.
Also, I can settle the flame be leaning the canister slightly while upside down. I am using mostly-empty canisters. However, as soon as I tip the canister fully upside-down, the stove fireballs again.
As I see it, I can cut a new blocks and hope for a better fit and/or make the fin out of copper to increase heat transfer. I also think I should add a thicker rod inside the brass tube to decrease gas flow.