Here's a bunch of random tips that might help people get better results setting the hover manually (without using the plastic tool). There might be a legitimate issue with some bases so your mileage may vary but if you're stuck and can't get it to work, here's what I've learned after a week with mine. I can probably make a video too if there's demand.
Short version
• Enable the Delorean lights first, hold the car gently with your fingers under each door and lower the car slowly onto the middle of the base until all the lights go solid but not so close that the car slams down. This is the sweet spot.
• Repeatedly lift/lower the car over the sweet spot multiple times (never more than 5 seconds per attempt) until you have an attempt that feels "clean". To me it feels like resting the car on a cushion of air and you can kind of feel it gently "plop" down without the magnet pulling it all over the place. That "clean" feeling means you can let go and it should hover. Take note, you WILL mess this up a bunch of times and WILL get used to prying the car off the magnet (gently).
Long Version
• Hovering the car is like lowering it straight down onto the head of a pin or like trying to balance it on top of a ball. Think of it this way when you're attempting to hover and it will help you learn how/when to let go.
• Get used to finding the hover point (or "sweet spot") by enabling the Delorean lights first. They can be turned on via the touch switch even with car removed. You can't tell if they are on until the car is close to the stand but if they are, you'll see the lights fade in/out depending on how close you are to the sweet spot.
• Hold the car by placing your fingers just below each door and gently/slowly lowering from directly above the sweet spot. Again, like you're lowering it onto the head of a pin.
• As you SLOWLY lower it, you'll feel the car wiggle/pull in various directions if it's not perfectly centered. I call this the "wiggle phase" and if you get too close to the base or too far off the sweet spot, the magnet will pull it hard in a random direction. This WILL happen many times as you learn to do it. Carefully lift one edge of the car to separate the magnets and start over.
• Do not spend more than about 5 seconds in the "wiggle phase". Trying to make a bunch of micro-adjustments while holding the car above the sweet spot just doesn't work and eventually it'll slam down on the magnet. It's much better to lift it up and start another attempt, again using the Delorean lights as a guide (brighter = closer to sweet spot).
• You'll know when you're getting close because the car wont "wiggle" as much as you get used to finding the sweet spot and the lights will be perfectly solid.
• I find the best results are when you start over and lower it straight down onto the sweet spot. If you hit it in one shot, the car doesn't pull and you can let go and you're done. If it starts pulling in various directions, you MIGHT save it but again, I find it easier to just start over. Hence the 5-second rule.