I'm not sure what you mean, you have to customize the USB Drive Installer to make it work on your hardware, if you include the necessary kexts (and voodoo kernel if needed) you should be able to boot the USB Drive installer on any computer. I just explain the basic procedure, you have to find out the kexts if your hardware is very far from vanilla. To make the USB installer completely universal you would have to include kexts for all of the hardware you want to support, at least for the storage controllers.
From there you can install any place you want, be it a fixed SATA HD, IDE, or a Firewire or another USB Drive, if thats what you mean with portable.