Moderator Note: This thread is a continuation of a discussion that started here.
Dave is of course, quite right. My response was purely about the 'safety' of a female overnighting at truck stops.
On the other hand, with a little bit of ingenuity, it is possible to be very comfortable in a smaller vehicle. (Mine has a bed, fridge and storage as well as a camp stove.)
Recently I have seen two instances of people sleeping in smaller vehciles, probably as small or smaller than a Yaris. One was a very small SUV, a bit like the Yaris. Only the driver seat was still in the car. On the passenger side there were storage containers with a small single mattress on top. May not suit a six footer, but the owner was far from six feet. This was a roadtripper who had it all worked out.
Another was a sedan, Toyota if I recall correctly. It had somehow the passenger seat down and its owner slept with feet into the trunk storage space. Have to say it looked pretty comfortable with a full length mattress on which to sleep. Unfortunately, this person was forced to live in a vehicle, having lost everything else.
It can be done, but I agree with Dave that you need to be comfortable to get a good night's sleep.