[an entire row of seats, pull up the armrests, steal some of those pillows and blankets that smell like shrimp and make yourself a true lie-flat bed, easily rivaling anything in first class?
A bit of a stretch, mate!
Ah, well,... I can tell you; several times I've managed to TRY to sleep while spread out in coach in rows of seats of various lengths, but always ended up feeling poked in the ribs with the remnants of a seat-belt protruding from the edge of a seat , cramped under an armrest that rose only so far , or crick-necked because my head was jammed against the aisle-side armrest. In some cases I finally just lay down on the floor, but the FA's would come along and nag when the flight deck wanted everyone to buckle up.
But I've never been so comfortable as in first class on transpacs, where I truly DID manage to sleep, and to arrive in Bangkok able to function--instead of feeling nauseated and jet-lagged for days.
Good luck, though: YMMV