shouldn't be a problem. I've folded the seats on my Prius flat and lay down on it for an hour or two before. The indent on the seat will go away after a day. At least it did on my Prius.

Mods: EV mod, VVT-i emblem, sport pedals, OEM cargo mat, JDM Prius interior footwell lighting, Sylvania Silverstars 9003ST, DICE iPod kit, OEM all-weather mats, TomTom ONE v2, LED licence plate lights.