Well, thanks to fuel costs lately, it's the small cars that are most likely to be sold out, not the big ones. So, a PC renter with an F booking will likely have a pretty good pick of the litter.

When you arrive, I'd be willing to bet that there will either be a very large sedan (Crown Victoria, etc.) or an SUV in your stall. Either of these will be just fine roominess-wise, although you might want to peek around and look for a minivan, just so the kids can spread out a bit. Lately Hertz has been foisting minivans on me when I have smaller-car bookings, so when a PC shows up and is willing to take one as his upgrade, they'll probably be happy to give it to you.

My recent Canadian rental - 3 weeks ago in YUL - was a station wagon (Dodge Magnum). It was less roomy than you'd think - plus difficult to see out of. If you get one of these in your stall, I'd recommend asking for a Crown Vic instead.

Well I believe the Magnum is a E class (station wagon) so if they gave you that on a 5* F reservation, I consider that more of a downgrade then upgrade.