The plastic corner pieces are so gianormous, they dont lend themselves to being replaced with steel. They are flexible though, and pretty cheap if they do need to be replaced....

We'll keep thinking about this, but no satisfactory solution has resulted yet.

Thread w/ pics and info: http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=60;t=000316