Double sided tape is reasonably good for mounting contact microphones to very flat smooth surfaces. It is better to use it in conjunction with
poster putty. For maximum strength I recommend using a layer of double sided tape on the surface, then some poster putty, and then another layer of double sided tape on the mic. This is very strong, I once pulled the veneer off of plywood trying to get a microphone off of it after sticking it on like this.
