Which way are you doing it? Because if you right click on your clip while holding ctrl and move it to the left it will speed it up. If you want it to go even faster right click on that same clip go to "Insert/Remove envelope" and click "Velocity" and move the green bar up. Those are the only ways I know and it gets the job done for me xD
Did it for this video! (haven't one a speedpaint in a year orz//)~