to shape the foam I used a 4 " grinder for fast removal, then used a belt sander to smooth and finish the foam,. left the outside edges square when you stretch the vynal it pulls it down , to a nice finish, and good for us over 200 lbs. I cut the dome off completely and ran the foam over it, when parked putting your helmet in there just push the seat down , still gos in and closes,. I used 4 " 10 lb. foam, and cut a slant in seat were I sit the most so I dont slide forward any more,. A 1 " slant did it,. by the way wear a face mask the foam flys with the grinder , and turns to dust with the belt sander,.