I made my own panniers and supporting rack. I was shooting for the 32 inches or so that the handlebars measure, but ended up 1 inch wider. This is fairly tucked in with an aftermarket exhaust that allows for a bit more clearence on the left side - I was able to get the same width both sides. Mine are square, so a bit of loss in volume over Grant's, which conform to the space allowed more efficiently. 40 litres per side, wouldn't want them much smaller, but this is fine for solo. A solid rack is really critical (and sub frame!), more so then saving a few inches in width I'd say.
OK small correction: after making the above statements, I thought I'd better make sure! the handlebar width is actually 33 inches, or 34-35 if you factor in that the brake and clutch levers stick out a bit extra - to that is your 'minimum' clearence distance, although practically you can get through narrower spaces like doors (important) by twisting the bars. my panniers mounted come out to about 34 1/2 inches, or 88 cm.
[This message has been edited by Timo (edited 16 February 2003).]