I just fitted the Mantis full kit to my MMR all good except for the Merlin hole, I bent it as suggested to get it in and then bent it back once installed to get a flush fit. But I found that my ball eject solenoid runs so close to the edge of the hole that it hits on the protector, there was no way to adjust this, no movement on the solenoid mounting to give it more clearance and the protector was sitting as snug as it could go.
So I have removed it and after multiple bends to get it in and out and even trying to manipulate the protector where the solenoid travels the protector is looking a bit shabby now so I think it will just go in the bin.
IMO this was not an install error on my part as there is just not enough clearance to allow the protector thickness.
I'm going to order a Pinbits Merlin Hole protector instead, I know that doesn't quite do the same job but it's best I can do.
I'm happy with all the other Mantis protectors