I distinctly recall flying PDX-EUG a number of times on UX in the 1980s on a small plane that was boarded from the rear. I recall as you enter that there was an open closet with elastic strapping to put your carry-ons (no overhead), and that the aisle was sunk lower than the rest of the floor of the plane. About halfway up the cabin, there was - what looked to be - a place where the plane was bolted together and where you had to step over a 5 or 6" hunk of metal in the middle of the aisle.

Any of this ringing any bells?

What type of plane did I fly on?