I may be wrong but 2 points from my opinion locker:
1) Glocks tend to run most reliably when left alone.
2) If you think adding 1 extra round to an already anemic magazine will save your life, think second magazine instead.
Id love to have a 43, all the pocket guns will be single stack with low round count... its how it works, cant get around that. Id rather have peace of mind knowing it will work 100% of the time rather than have after market stuff on/in it.
Its your gun, do as you wish... but they are points to ponder.