Dear tsuwm: sounds more appropriate than most of the ones I saw. However, can you give us a bit of explication?
This has to be medieval French. I don't see any imperative verb in "séant" . One of the banners I saw had two knights on one horse. I wouldn't call that "sitting pretty". And many of the sites I saw associated the motto with the eight pointed cross. How does the motto fit that?
The text I read had student notes, but I didn't feel like joining the club, so I saw only the notes included with the text at:
http://pd.sparknotes.com/lit/ivanhoe/section4.html