It may work to launch from the roof of a car, but the steel roof will very likely confuse the drone's compass, and this will produce a warning to re-calibrate the compass. Sometimes I see this when I launch from a rebar-reinforced concrete deck. The Evo is pretty sensitive to nearby steel.
If you have solid GPS and compass locks, and are using a distinctly-patterned and contrasting landing pad -- the Evo can RTH within a foot of its take-off point. This also requires slowly taking off straight up to ~40 feet before leaving the area ...giving the drone a chance to photograph and 'remember' its home point. Even still, there's no 100% way to ensure a dead nuts landing every time with RTH.
Personally, I see RTH as an emergency backstop -- not a convenience or a source of entertainment, and I almost never use it. If the drone loses connection to the remote controller, it's nice to know it might return home. But that's about it.