Sorry for the relatively late reply—I got here as fast as I could!
Originally Posted by mchan8
There's really no way to automatically ensure that any given app displays the iPhone version instead of the iPad one, as there are plenty of ways to detect which device you're looking at.
However, most sanely-coded apps can be taken care of pretty easily; just find the app's Info.plist file through FTP, iFile, or some other means (it's located at /var/mobile/Applications/[something]/[app name].app/Info.plist) and open it with an application that can edit .plist files.
Then look for the following:
This part of the file simply represents what devices the app natively supports—1 for iPhone, 2 for iPad. Just delete the line "<integer>2</integer>" and most apps will be tricked into showing their iPhone version!
(That's your best bet, but if it doesn't work, then like I said, there are a number of ways to detect what device is being used—if you'd mind sharing what app you're trying to get working, someone here may be able to help further).