Like what was shown in the video they sit slightly proud vs the magsafe .6 mm to be exact. You won't be able to see it, but you can feel it with the mat.
Sizing wise it matters. So yes the official pixelSnap chargers or apple magsafe ones are the only ones that will fit. I have some other ones in route to me now. As long as they don't suck, we will begin selling them.
Since David (other half of Soonish) still has his Gen1 we are doing the install on his truck. Should be within 2 weeks.
I installed the system on my Gen1 before I traded it in. Works beautifully with the Meridian System.
Can't fit anything else into the stock cavity. Let alone the OEM amp wouldn't be specced for it. This isn't a crazy install. Some people may think its a crazy install but its really quite straight forward, and not crazy in anyway.