I've had quite a few questions about the rear bumpers and heard a lot of rumors about changes to the rules. They have made some clearification but it seems the rules stay the same for the wider bumper.
The IKFs web site front page has a posting for the April IKF board of directors minutes. Please follow the link to the IKFs web site and down load the PDF file that has the detailed minutes.
http://www.ikfkarting.com/ (this is the home page)
http://www.ikfkarting.com/OfficePages/PDFs/MeetingMinutes/2011-04-BoardMeetingMinutes.pdf (should pull the PDF)
The IKFs web site has a wealth of information and is a good source for updates such as this.
Let me know if you have any questions.