Been using foam mutes since the 90's. I just use the grey foam that comes in things like Pelican cases and similar. The density is right for what I want to achieve. Sponge can work too if it's dense enough. I try to cut it as narrow(vertically) as possible and shove it as close to the saddles as I can to minimize intonation issues. I often play with a pick and thumb thump with my hand down by the bridge(even when using foam I still palm mute for varying degrees of decay) so the Nordy looks like it would get in the way of that bizness.