ThomasC, I'm a little rusty on the tones (I'm actually more familiar with Cantonese), but I'm pretty sure Guo is the falling tone and Xiong is the dipping tone. If it helps Guo is "nation" and Xiong is the second character used for "hero." Obviously my grandfather had high hopes for me .
The pronunciation is correct. For those who aren't familiar with the Mandarin-class-sounding-out regimen, this might help:
"Guo" is basically putting "gw" with the "o" sound of orange - more or less "gwô"
"Xiong" is pronounced "sh-ee-ohng" with the "ee" very slight and quick (most would probably not even catch it).