Right now I have a post type that generates a slug, e.g. http://url.com/l/abcd/ for each entry. I have a query in my 404.php that checks for http://url.com/abcd before output and redirects it if found in that post type "l"... What I'm wondering is, since 404.php will always send a 404 http header, is it not ok to do 301 inside 404.php (before any "output" starts)? It "works", but I suspect there is a better way...
Is it a bad idea to do a new rewrite_rule() for every slug in that post type? Is there a way to make post type "l" be top-level or checked "along with" page slugs?