I just use plain old kitchen foil, no adhesive necessary. It's not something a manufacturer would do, but it works fine. Never had a single problem out of any of the dozen or so I used it on, including my own basses. Remember, you're not trying to hermetically seal off the wood, you're electrically shielding it. Under the pickguard, if your shielding is done right, it will never move anyway. Just press the foil into the wood to the point that it forms to the shape and make sure all your grounds terminate to it directly. If the hum changes relative to your amp, it's the amp, not your house wiring giving off the RFI anyway. Some noise at very close distances is normal, but not at more than a foot or two away. I'll bet money your bass probably has a cold bridge ground. The pickups are grounding through the amp circuit, but the shielding/grounding is not tied to them well, making your bass hum.