We always have an Intermediate car from Dollar (in 2003 we had a Saturn L200, and in 2005, we had a Dodge Stratus). To be honest, even for just the two of us, when we took our older shape hard plastic cases, we only just fitted them in. This year with two softer, new shape cases, we had no trouble fitting them, but I wouldn't like to attempt a third case in the boot. One on the back seat is fine as the cars a quite big inside. To be honest though, even a 'Full Size' wouldn't be much better, as its still a saloon car so boot space is limited compared to your typical British hatchback. With 4 cases, I'd be considering upgrading to am SUV, or one of the Dodge Magnums (an estate car) that I've seen at the Dollar depots recently.