Why wouldn't you put it back? It's just soldered on there. EMI with other components possibly. I think installed that area sits immediately under the back of the yoke. Might have some field effect issues.
I've run them with and without the cover, I've never noticed any difference at all.
Currently Owning: Vids- Road Blasters, Road Runner, Joust, Golden Tee 2005 Pins- Back to the Future, Theatre of Magic, Joker Poker, Grand Tour, Hyperball
Previously Owned: Vids- Far too many to list Pins- High Speedx2, The Shadow, Mystic.
TSPP is here!! STTNG on the way! Tommy Stargate High Speed Genesis Aztec
Off to other homes to be enjoyed...Freddy a Nightmare on Elm St, Pinbot, F-14, Robocop, Monday Night Football, Flash Gordon, Mr & Mrs Pacman, Meteor, Jurassic Park, Grand Lizard, City Slicker, Baby Pac-man, Wheel Of Fortune and T2 has moved on...man I miss these things when I sell them!