That was my first winter project here in Maine this year. I love the look. I used an electric knife $9. 1) I went straight down the back a little to provide a slight back support 2) I dished out cheek indents
3) then I tapered the sides a little where my thighs hit the seat. Remember a little goes a long way and before I cut anything I maped out where I set on the seat, where my legs were both on the bars and boards, did a lot of measuring and grafting on the foam with a felt tip marker and then went at it. Scared the crap out of the wife and had threats of no new seat if it doesn't go well. One issue was on cutting the back support...on the sides when I reinstalled the cover I got a slight wrinkle on one side. I'm waiting until spring and then I'll try to strech and pull it out and re staple that section. all and all I love it. Of course the first long ride will tell. Two feet of snow yesterday so may be a while yet.