said by Oh_No:That is why you subtract the over head from your sync rate to get your absolute max speed. Then you enter in that max speed into DD-WRT and your problem is solved.
Then what would ddwrt do when it needed qos to kick in? If I tell it my absolute max speeds which is about 14 megabits download, it has nothing to work with for QOS. The way they instruct you...I would need to put max of 12 mbits so ddwrt had 2 mbits to work with. But the problem is, my max speeds all the time would be 12 mbits which is hardly ideal.