On the Tatone Peacepipes, I've found the chamber size understated. The .09-.19 is best suited to .10 and smaller. Am using one on my Enya .09-III TV. Am using the .29-.40 for my Enya .19-VI TV, works fine. I bought several .45-.65's, those I'm reserving for the .35's to .45's. I don't know if I would use it on a .60 though.
I suppose one could stuff them with steel wool similar to glass pack mufflers, but I haven't seen the need for that. In my use they seem to provide ample sound dampening without resorting to additional acoustic materials. I've seen some with exit tube cut off for a larger opening, got one I received just like that. Now that might be noisy and require taming.