I'm 6' tall, with a 36" inseam (i.e. short torso, long legs) and 105 kilos (i.e. I weight too much). I've been riding the Nozomi, Hikari, Hikari RailStar, Kamome, and Sonic trains for the last 3 weeks and have found the regular seats to be just fine. I haven't been tempted even once to pay extra for the green car.