The easiest answer may be to substitute the original internals with a straight-through perforated tube to make it the same as a Burgess, and pack some rockwool sound absorbent material loosely around the tube. Dead easy to change the wadding when it gets oiled/carboned up. I have a big file of the drawings of Scott parts that John Underhill drew many years ago. There MIGHT be a Howarth Drawing, and will have a look when I get chance. I’ll let you know if anything turns up.