Problem keeping resource files for iPhone/iPad builds in sync

Question

I recently created a new target for iPad by upgrading my target for iPhone, which seemed to work fine. However, since then I have had problems when I make changes to the plist files that I have grouped under Resources.
When I upgraded the target, it created a new folder for iPad resources called Resources-iPad. This only contained the nib files -all the other plist files I have containing data are still in the Resources folder.
When I added a new plist file to Resources and try to load it using the bundle path, it gives me different paths for the iPhone/iPad versions, in .../Application Support/iPone Simulator/4.2/Application/...
However, the path of the file I am trying to load is of the form myApp./MyFile.plist, and I can't seem to open the app in the bundle path directory in Finder.
I've tried things like making clean, etc. Are there any steps you need to take to keep the resource files of the iPad target in sync with the iPhone one once it has been created?

Answer 1

I created the new target using Xcode>Project>UpgradeCurrentTargetForIpad. This created another folder under .../Application Support/iPhone Simulator/4.2/Application/... with a different serial number. The new folder contains a new app, myApp-Upgraded, which corresponds to the bundle path it will use when this target is run.
I presume it's due to the file path existing in the original app, but not in the upgraded one. The file will be found when the original target is run, either on the device or the simulator, but not when the upgraded target is run on either, but I don't know how to make the upgraded target reference the correct resources.