I was at Home Depot last night pricing things out and I don't think it's going to be any cheaper to use pink insulation. In fact I think it might be more expensive and more complicated.I hope that allays a few fears and makes things a bit simpler (and cheaper!)
Can you provide any links to traps that have been built like this? I did a lot of google searching last night trying to find examples of people who had built traps with pink fluffy stuff, but couldn't find any. In fact, most of the results I found where people saying not to use it. Examples include: "The pink stuff is good for in the walls only. Completely useless for bass traps or diffusers", "you need density for bass traps- the pink insulation(probably wall or ceiling insulation) won't do much for you", "The pink stuff just isn't dense enough for bass traps. You want something like Owens and Cornings 703 or 705".What we have proposed is not some abstract concept. It has been done many times in reality, for substantial savings.