I'd remove the bracket, slide the coil/bracket down, toss a locknut in the bottom of the coil. Reassemble. You shortened the plunger stroke and no more hitting the playfield.
You can also open a ticket on the support desk and ask for the longer plunger to prevent this.
Either method works, neither effects game play or slingshot action.
I prefer throwing a locknut in. You ever work on it, you'll remember it and reuse. If you have a longer plunger and replace it years later, you may forget the plunger is longer and stick a regular one in.
LTG : )