Agree that light rims won't make a noticeable difference.

Besides having the power to make the jump, you need to have good threshold power. If you don't, you are burning matches just to stay in the group. Do that too often and you won't have anything left for the sprint. One way to keep from burning matches is to be smart about positioning in the pack. Don't be in the wind, don't leave a big gap to the next rider, be on the lee side when there is a cross wind.

Also, if your reactions are slow when the sprint happens then you have a larger gap to cross. Learn to anticipate when the pack is going to jam and get on it immeditately. If you react quick and hit it hard you can stay on the wheels without much more effort.