I second the tape around the edges of the playfield glass.
As I not only fitted a shaker motor to AC/DC but also a massive powered internal sub (almost no need for shaker motor).
To start with the glass rattled like HELL (pun intended) so I put some anti-rattle tape to the edges of the glass and hey-presto no more horrible noise just tonnes of bass and air being blown up by my hands where there are gaps between the lock-down bar and the glass.
Awesome