I'm using right now version 7.4 on a 16 Gb USB pendrive which I made with pendrivelinux from KNOPPIX_V7.4.0DVD-2014-08-01-EN.iso a few hours ago. It works as long as I don't try to use any cheatcode on boot.
This post is being made from this version of Knoppix. I have got a persistent home of 4Gb.