The DVD firmware mod does work once you get the DVD to burn properly. It is not new and has been documented on numerous forums over the past two years (
here and
here just to name a few).
I have tested it several times and confirmed that you do in fact lose some functionality, which is to be expected since they don't upgrade the firmware just for fun. For me this was a deal killer since the AUX jack on the dash never worked with the downgraded firmware - you could plug something in but the AUX switch never enabled the device to play through. I reverted back to 6.1 and the AUX worked fine again. Also, you had to manually enable the bypass function every time you started your vehicle, which to me was as much or more of a pain than the occasional function block while in motion.
I had started to compile a list of the other functions and screens that were missing or limited after the downgrade but then I scrapped those notes since it was quickly apparent that I did not want to use the old firmware under any circumstance. I reverted back to 6.1 and now I use my wiring mod to bypass the motion lockout for 30-40 seconds with just one flip of the switch whenever I need it. Soon I will have the pulse generator circuit completed and then it will be a permanent mod and no need to even flip the switch. My advice would be to go ahead and wire a toggle switch into your speed sensor line - cheap, easy, and ultimately just as effective without having to downgrade your firmware and lose functionality.