1. Conduct all tests outdoors. Pressurized stoves might not explode, but things can go wrong. Tape or glue can fail causing parts to separate and spew flaming fuel surprising distances.
2. The plan for what you term 'double wall' escapes me. Do you mean a Trangia type with a central well? Seems unlikely if you are planning to use a priming tray and filler hole. Or are you describing a variation of the low pressure side burner stove which usually has an open top that is sealed by placing the pot directly on the stove which is also the pot support. It sounds as if you plan to have a closed top and a filler hole. If that is the case, you may have a problem:
If the flame jet holes are too large in a sealed stove (using a screw-closed filler hole), the flames can ignite fuel and residual oxygen INSIDE the unit. It might not explode, but it can definitely cause more excitement than you want. Therefore, more small holes are better than fewer large ones on sealed pressurized stoves. Check ZEN stove site for hole sizing for pressurized stoves such as the Photon and the Penney.
3. Do you plan to use the large Sterno can or the small one? Pressurized side burner stoves tend to push their flames out pretty far. If you use the large Sterno can, the heat may largely miss the pot. Furthermore, the large can has a greater potential for uncontrolled and unexpected excitement because its larger volume in relation to the amount of fuel means more oxygen inside the stove to be ignited if a jet wears too large or if you have a leak somewhere. Again, don't light these puppies inside the house.