Instead of soldering 2 sheets of copper tape can you fold over one piece. Touch the copper from one sheet to the folded copper of the other sheet and attach the 2 pieces with a very small screw?
I was under the impression that the copper shielding tape is conductive on both sides...why do you have to connect pieces with a screw or with solder? Curious, as I will be doing a shielding job on my bass later this week.
If the copper is of sufficient thickness then it's not an issue and should work fine from a conductivity standpoint. If it's the equivalent thickness of tin foil then it will likely tear over time.