I have seen on here before people complaining about the carb rubbers and clamps from Dave Silvers.
I have just renewed all the rubber boots on my 550 and they have fitted no problem at all, I kept them in the airing cupboard for a couple of days and they were beautifully soft and with a smear of fairy liquid they went on a dream. The clamps from DSS though are a different matter as they seem sooo soft and will bend and become misshapen very easily. I went to HCL clamps and got some 9mm wide worm drive clips and these are perfect for the job, needless to say I have no intake leak at all now and the bike is running as well as it ever has done.