Keep in mind that the Vista Cx does not have the new SiRF chipset like the other Garmin "x" models. I have a 60Cx and it is MUCH more sensitive than my older Garmin GPSRs. I can get and maintain a lock under tree cover, down in deep canyons, inside shopping malls, etc... It is a huge advantage for the 60Cx, and made the increased size less of a factor for me.

You might also want to ask your question at the Groundspeak forums

http://forums.groundspeak.com