It does depend on what unit as to how the CX displays in Map Info, and the various combinations for various device series is explained in the Garmin link [refer [Only registered and activated users can see links. ]]. Sometimes de-delecting the CN can still produce problems but it's rare. That's when you need to revert to separate media cards for the CX & CN.
The biggest mistake users make is to use non-matching versions of the small [MMR only] cityXplorer and City Navigator. For instance teaming small 2014.10 CX with an earlier or later version City Navigator. Although that's a common problem it's not covered in the Garmin info because Garmin doesn't produce any 'small' CX map without it's own CN data in the file.
Thanks for the tip for using an external battery pack for CX use. I suspect the main reason Garmin didn't include pedestrian mode in the new 2013 devices is because of their very short battery charge life. Another useful way to extend the battery time is to turn the display brightness right down when you don't actually have to refer to the screen, like walking a long street or when on public transport you can even turn the unit off.
I cannot let your info about being in an 'ummmmm' neighbourhood in Amsterdam go without comment. I guess once you got where you were going it didn't involve much walking .....