"Obviously power will need to be altered when the barrel length changes,"

are you shure ?
the longer barrel for my tdr gave my an extra 1/2 fpe which brought it up to being "low"

the cyl on mine unscrewed easily (once empty) no trouble,
id taken off the end filler and reinserted it so as not to crush the open end,

as always heres a couple of pics ..
both cylinders with gun
and pre chamber

JASON..