It does not need louvers. Drill some holes. I don't think originality at that location is needed. You can not punch or die squeeze a louver because you can't access both side if already welded. You can't cut a louver shape and bend without extreme careful miniature work. (small Dremel burr tool).
When you drill thin sheet metal ALWAYS use a step drill.
If patch panel already welded in place and you really really really want louvers, you can make some and weld them in or get your old ones and weld them in. If you make them you will have to make a die set first.
If you don't like holes, cut 1/8 slits with 1/8 holes at the ends.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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