Leave it stock. Like others said ... the plastic has flex built in as was designed that way on purpose. The stock plastic rod will last for thousands and thousands of rounds and will cost you $5 to replace it. Why mess with that?
Those after market rods are a solution without a problem .... looking to create a problem the original solution already fixed. Did that make any sense?
The stock recoil spring assembly costs $5 - $8. The plastic rod will outlast the spring that's on it.
Aftermarket metal guide rods cost $20 & up, replacement springs for them cost $5 - $8. The ability to change spring rates is an advantage for gamers. If you're a casual user there's no advantage to using other than the factory spring rate.