If by 'fine' one refers to having proper scale length and width such that the will fit, say, in Kato Maxi IV well cars, then yes they are fine. Unlike, say CC 40' containers and Deluxe Innovations Twinstacks.
As far as looking right, the Con-Cor 53' and 48' containers seem to be based on a 90's-era Monon sheet post container. Their pretty accurate representations for certain prototypes as long as you don't literally count the rivets, and don't mind them being approx 4 scale inches too short in height.
http://www.matts-place.com/intermodal/part3/images/apcu530582.jpghttp://www.matts-place.com/intermodal/part3/images/apcu530313.jpgThe photos show paint schemes that I consider to be models of the actual prototype, or close enough. That's the 48' and 53'
white APL scheme, and the 48' BN America scheme. Some others that CC has done that are 'plausible' (which is to say that the companies could have owned such containers, but I don't know they did) include JB Hunt (both sizes), Southern Pacific 48', and Conrail Mercury 48'. Santa Fe would be all right, but I don't think CC actually did that one.
Along with similar containers from Deluxe, you can get a sense of the prototype variation among 90's sheet post containers, which of course were mostly 48' not 53'. However with respect to JB Hunt, that plausibility really only applies if you're modeling the 90s, not the 21st century.
With respect to the newly announced paint schemes, and many others that CC has done over the years, they are do not closely resemble any prototype containers that actually carried those schemes. Sheet-post containers are a much smaller percentage of containers than they used to be. So most of those schemes really belong on corrugated, exterior post, or plate wall containers. Newer sheet post containers tend to look substantially different with far fewer rivets, if any.
