I use my approach ramps for my lift. They are made of aluminum, approx. 5 feet long and achieve a 4" lift. There is no way you can drive a viper or a c-5 vette up any of those ramps you are describing without serious contact. If you use the ramps I am speaking of, you must create a solid landing pad with a stop. I use this method currently because my cj-7 frame off project is still on the lift. Anyway if your handy, the easiest, safest method is to make some very very low profile step ramps out of plywood. These are very similar to what people use for their motorhomes for leveling purposes, only much longer. You really don't need much height to do an oil change. If you need pic's I will try to figure out how to load them on the site.