Cat has also revised the shape of the belly pan to allow more forward room for the rider. With the added two inches, you are more on top of the weight of the sled.
By dropping the drive shaft a little over an inch, Cat has lowered the approach angle of the track allowing the M 6000 to get up and stay on top of the snow much better. It also increased the track-to-tunnel clearance to three inches which allowed Cat to use eight-tooth drive sprockets … which again provides a flatter approach angle and improved floatability.
Part of the process in perfecting the Mountain Drive System was to eliminate as much weight as possible to free up the power for performance via instant response. You can’t be quick and nimble if you’re packing an extra 15 lbs.