Here’s the trick. First, build your universal binary, let’s say under Debug mode. Then from a terminal …
cd build/Debug /usr/bin/arch -arch ppc MyApp.app/Contents/MacOS/MyApp
This will launch your app using the Rosetta PPC emulator. This way you can test your Universal binaries from an i386 system
I’m doing it this way, because for some reason the ‘Right Click on Your App > Get Info > General > Open using Rosetta’ checkbox is grayed out. Oh well!
P.S. Another technique is to go into Project > Edit Project Settings > Build > check ‘Build Active Architecture Only’ .. Then you can change your active Arch to PPC and the build will only include PPC and will run. Just be sure to uncheck the box before you send a build to your users.