Change AVC level without reencoding

Hi everyone,
I've searched through the archives, but haven't found a solution to my problem.

I have an MKV file with AVC level 5.1, which I want to change to 4.1 or 4.0, but I wouldn't like to reencode the entire file. I found a nice program for Windows that does the trick in less than one second (IDC multi changer), but having to reboot into Windows everytime is a bit messy. Does anyone have experience with any software that can do this? I've had a look at MKVTools, FfmpegX, Handbrake etc.

Thanks!