I've looked into this also, the brakes on the M suck its as simple as that. There underpowered and heat up to quickly when riding hard, once that happens they make noise. There are some things you can do to better them like already posted here, Adjusting rear brakes properly for the rear, (not to sure about using the hot to the touch method), and for the front you can upgrade the pads and use steel braided brake line. Now take a look at this, im sure some of you have already seen this>>>>
2008 Suzuki Boulevard 400 specifications and pictures
Note were it says rear disc brake.. Its the same bike just with a 400cc engine, im sure with little modification it will work, but is it worth the $$$?