I have fitted the retractable strings to my Rocco, just . Not too bad, but needs a bit of drilling, a hot glue gun.
Picked up a set of retractors string things from the bay for £5, and drilled the shelf out.
Used the HG gun to fix the mechanisms to the underside of the shelf. All good now. Managed to remove the dongle things whole too.
(there is a plastic key that holds the rubber ball onto the string thing)