I already know my ramp is going to have to go out about three feet, have a platform, and andgle back again because there's only about three feet of space infront of my pop door to my run fence and it's about 3 and half feet off the ground so straight down will be too sharp...I also cant have the combination of the two ramps be more than about 18" because than it will block the walk in door...what's the minimum I can get away with if each peice of ramp is about 2 and a half feet long? I was hoping I would be safe with 6 or 7 inches...