IMO,
I would not use brazing (heat) for a repair such as this. ..you may find that drilling the holes left a burr or high point around the hole, filing it or dimpling it will provide some "extra" hold for the filler. If you do not do this there is no way the Bondo will a stay in place when sanding the filler down. etc.
Find a small peening hammer or pick/scribe and just barley dimple the hole to allow for a thin layer of filler to adhere to the frame.
If this seems too drastic a solution (SMALL dimple), then I would find a suitable sticker or reflective tape and move on, watch for stress fracture (not likely) and it they occur us the more aggressive solution.
Best, Ben