might be able to have your cake and eat it. Drill out the rivets to remove the original sleeve - that way you can always keep the originals as new if you eventually sell the bike.
http://www.arracing.co.uk/anr.nsf/vi...xhaust+systems courtesy of Antonye.
scroll to the bottom of the page for "spares". Not sure if they have non-round outer sleeves though.
cheers, Chi
[Edited on 5-5-2005 by chicken]