Install Mavericks on Unsupported MacBook 4,1
@Thinkling You were so close...I'm currently running Mavericks 10.9.5 on my Blackbook 4,1 Early 2008. Here's how:

Make a plain USB installer by using DiskMaker X, but after its complete, navigate on your new thumbdrive to: /System/Library/CoreServices/PlatformSupport.plist and completely delete that file.

Boot holding option key, select your thumbdrive, and install away.

Worth Noting:
I had to install the kext file for my graphics (Intel GMA X3100 144 MB) to work properly, and I'm still fighting a no sound issue, as well as machine not sleeping with lid closed. Other than that, I've got Messages working, and haven't had any other issues in the month i've had it installed....