I've run both the M-1s and the Z-6 on my '03 Lemans, as well as the M3. I like the feel, handling and cornering ability of Metzler tires, but the M-1 is just too soft to run on the rear of a V-11, unless you want to be putting on new tires all the time. All that Guzzi torque out of the turns, you know. I am not an aggressive rider, but I got only 2800 miles out of the M1 on the rear, and handling ability was actually compromised significantly after 2000-2200 miles. The front M1 provided 4500 miles of wear.
Sure, the M1 is a sticker tire, but if handling is compromised that quickly it ain't worth it, especially considering the cost and hassle of changing tires. (Of course if I worked at Moto International…….)
The current tire configuration on my V-11 is M3 in the front and Z6 on the ear. This seems to work just fine. May try Z6s all around next time.