What light planes DO have nice backseats? Also, if you are below 200hp, you
are unlikely going to need much room back there.

I am just shy of 6'3". Most planes become 3 seaters with me up front.

So far, I see a 182 is okay for a small person behind me, a Cirrus is okay
as well.

I would have to adjust my seat for a Mooney to work well. Haven't seen the
long Arrows, but the regular ones - forget about it. 172, no soap.

Diamond wins by far in this category because the front seats have adjustable
rudders, not seats. The back seats are rather spacious. Unfortunately, the
new ones have gotten heavy and now you really only need 3 seats.

Have not yet tried the back seat of the Lancair.