If you wish to attach hooks to the panel so that the appropriate chain length for its setting can be attached later, you need to use brass or other strong metal that can be securely attached to the frame of the panel.
An easy solution is to use brass chain links. Cut one link from a suitably heavy chain at the centre of the long side of the link. Straighten one part of the opened link with two pair of pliers or a vice and pliers. Solder the straight leg with the open part of the hook facing outwards, to avoid the chain (which is pulling inwards) from slipping out of the hook. The open part of the hook should give only enough room for the chain links to be inserted between the frame and the opening of the hook