this has sort of strayed from the point, look when it comes to safety forget it with these cars, they have no airbags, most dont have 3 point seatbelts, they dont have anti-locking breaks, etc....sitting in the front seat isnt exactly safe by modern standards... moving along i understand safety should be thought about for this scenario but the point (at least for me) of this conversion is for when there are three or four of us (were young adults but some of us are pretty small) possibly and my car is the only option for a quick drive, i dont need 5 point harnesses or recaro seats back there i just need something simple enough that they can put their but in and have a bit of back support to travel a mile or two, possibly less without them having to sit on that shelf behind the seats bouncing around, a seat would keep them in place a bit more but more importantly make them more comfortable, also if by chance a police officer is to stop us it would not look like we had just shoved two of my buddies in the trunk ....i was looking for ideas to see if it had been done before and to see if people had suggestions ( clearly people have safety suggestions..)