I've just fitted a Remus revolution and to get clearance on my Al Jesses I had to fit the Thick Spacers (1/2") ones to the front pannier frame rail mount, 1/2" spacers plus washer at footpeg mount, and extra spacers at rear pannier frame mounts (mounted indicator bracket between pannier frame and rear bracket., along with an extra washer spacing the exhaust can out from the hanger. With all these extras I've got close to 5~10mm clearance at the end of the can.
PS my Jesses came with the Adventure (or wide seat) spacers which are extra if you just got the plain GS Jesse mounts.
Iain Mac