I don't own the game but it sounds like you are trying to solve a problem that may not exist. Unless the flipper bat is taking damage to the point that you are replacing parts (other than the rubber) on a regular basis I don't think you need to alter your game.

Rubbers will wear and be hit (some much more than others). Order a few extra and change them more frequently as necessary. Think of it like oil in your car (more you drive the more you need to change it).

Drilling a non factory hole in your playfield to protect a 50 cent rubber seems like bringing a machine gun to a slap fight to me.

A post could create unintended consequences (change gameplay/flow in ways you don't realize at first). AT BEST you will swap frequently changing rubber on a flipper for a post.

Others that own the game may be able to chime in better to say if you have another issue going on? Misaligned flippers?

Lastly I'll mention if I was in the market for your game and I noticed you added two posts and drilled your playfield -- I would be a hard pass on the game unless it was priced insanely low. I'd wonder what other odd non-factory things were done with it and wouldn't want to buy it.

I think you are overly worried about the damage the flipper is taking (especially given the flipper is fine other than the rubber which is a common wear part on any pinball machine) -- and in any event I'd sooner replace rubber than drill holes in my playfield and alter my game. Unless you are cracking flipper bats on a regular basis it isn't worth digging into any further other than aligning *all* the games flippers properly and moving on.

One question we are asking is whether your other flippers are aligned correctly. Do you have photos of them as well? That could influence the angle and frequency of this shot a bit.

You seem convinced you want to do this (which is fine - it is your game to do anything you please to). You are overestimating the force. By a lot. Plus I'm not sure if you have done a flipper rebuild but know that *worst case* a flipper bat is $4 and a bushing is less than $1. I can't imagine what else would break and even those would almost certainly not break more frequently.

Buy a pack of flipper rubbers and move on.

Best of luck with finding a solution you feel comfortable with.

Consider Titan silicone rings too...
https://www.titanpinball.com/