This is old post, figured noone will read but want to mention somewhere. First though, I'd like to thank Toufiq for my outloud laugh at thier reponse to Lisa's request. There was a tear, I swear.
Any way, the reason I am posting this in old thread as I have just discovered why the soluion povided is not the best as applying an update to the Helix Framework will the error.php and the changes you would have made. I can undstad if there is no better solution, just thought would mention since I ran int the same issue when implmenting the proposed changes from the article.
You will also get the too many redirects if you named your Menu Item for the Error Page anything but 404. If you did, you also need to update this line to you menu ALIAS:
$redirect_url .= '404'; // menu alias - Change to your menu alias
Ah to think how many fish I coulda caught while re-doing this ;-)