To those interested in this thread with the compiled protector list, here was some recent experience.
Here's the list of protectors I compiled.
--Cliffy--
Catapult
Drawbridge protector
Shooter lane ball eject
Two switch slot protectors
PF flipper drain
Castle drain hole (not installed, went with Mantis)
'
--Mantis--
Castle drain hole
Castle protector w laser etched rock pattern
Moat eject hole
Merlin hole
'
--Pinbits--
Merlin hole
Plastics protectors (not on yet)
'
The Mantis castle drain hole protector was installed instead of the Cliffy version. Some people have said they prefer the mantis version protectors for new pins, but that wasn't specific to the MM castle drain hole per say. That one went on last as it looked ugly for install. In the end it wasn't that bad.
And interestingly, the merlin hole has two protectors in it; one on top (pinbits) and the other in the dished hole (mantis). Works great together, no issues here. Haven't even needed the rubber damper piece.
The plastics protectors install is more work and aren't installed yet, I'll pick away at it, but am in no rush since it's huo.
Everything went fine, no significant changes in game play, and it all looks great. Nice! And lots protected!
There is that new flat cliffy to protect the top of the pf around the moat, which I may consider, but I also have mylar and am leaning to using that for simplicity. Info here. https://pinside.com/pinball/forum/topic/mmr-protectors-mantis-or-cliffy#post-2654041