Looked it up and the compaq is 45mm longer than the other safe n sound car seats. not a lot but it may be too big for some smaller cars. As everyone and myself said, best to try it you can
well there you go an extra 45mm

I think the main benefit is the Base is a bit narrower and the sides too. It fit in my Lancer coupe just fine on the passenger back, fits my hubbies, nissan pulsar in the same possie and also fits my new Cruze.

I will say the downside to a small car is the car seats didn't fit exceptionally well in the middle , we tried it with all three cars and the fitting station suggested it would be better on the side so ours sits happily behind the passenger front.
From what I know about these seats in particular is that they are designed to fit the smaller cars, dunno how well they'd go in a mini or something like that though??!!