Anyone that's never been in a full lay down car won't know the sacrifices required to get there. The biggest issue , as Stainless said,
is getting your head forward far enough to see the land & thats where the collar-thing screws you.
I've been in the "Markley periscope tank", the driver position is not a full lay down, it's really comfortable & the periscope is bitchin. 30 seconds after you're in there, you don't even know you're looking through a mirror.
I liked the idea for the liner, but SCTA deemed it a no-no for a new car.
Sid.