Isn't the limit for the 'lip' supposed to be 1"? I thought I read that in the manual... I didn't get a chance to try out Summon in the time we had our demo car, but we have a somewhat-sloped driveway and a lip, and if we're to fit an X and a 3 in the garage, Summon may be the only way! I hope advances have it handling more sloped driveways, perhaps the way you can tell it to disregard tight spaces to an extent.