Hi,
I thought you might like to see what a Biker's Friend looks like on a Speedmaster. This is a Large bag (13 inch diameter by 15 inch long) which I think looks fine. I've got it sat on the standard seat and it is just the right height for me. I rode 40 miles through rain hail and sleet last week and it kept perfectly dry inside. The middle of my back was the only part of me that was warm and the bag gives your back a lot of support.
Here's their site if you want more information. I have to say their customer service was first rate.
www.bikersfriend.com Best wishes
Sid
