Mate,
I was thinking along this line some time back...what i came up with is that u go to any hardware shop and buy a flange(its a pipe with screw ) err how to explain ah...its two piece...one piece has pipe with thread , the ohter has a pipe with a screwable portion that connects to the other pipe then u screw them together to get one piece but its one whole pipe...i hope u understand...if not got to the hardware shop n askler..size can confrom to ur needs .....so wat u do is u weld each end to ur piping liao then screw and unscrew as needed...but then the exhaust muffler mounting should be removable wanler...not soldiried to the muffler...
speedz