Safe USB-Install

Hello

I am new to Suse and want to install it to an USB. I found this theard:

http://forums.opensuse.org/english/get-technical-help-here/install-boot-login/427135-opensuse-11-2-usb-hard-disk-install.html :

"Basically, it’s a normal install. However, you have to use the custom
partitioning - don’t accept any suggested layout for modification - to
ensure you only install on the USB drive and leave /dev/hda untouched.

At the confirmation stage, select change and write GRUB to the MBR of
the USB drive by re-ordering the drive list so that the USB drive is the
first and leaves the /dev/hda MBR unchanged. That allows you to use F12
or ESC (or whatever your system has) to select the boot device."

Now I want to know if this is really safe:
** I want to install Opensuse to USB without touching the built in HDD, so I want everything installed to USB! Meaning, that if I want to boot from USB I switch the boot
priority to USB in my bios. I want a real install, not a persistent live USB. Is the above described method really safe?**

I also found this one:
Jetchisel’s CyberCabin: OpenSuSE on a pendrive

But if the first method would work, I would be very happy, because the second needs lot of time.

For advise I would be very thankful!

Thanks