I've never minded wrapping my pinky around the bottom of the grip as the majority of my grip pressure comes from my middle and ring fingers. I have used pinky extensions that worked alright, with my P938 being the best example. However, if you get a reliable and functional extension that adds capacity, that's the way to go.
Honestly though, every capacity enhancing extension I've used on a carry gun made me wonder why I didn't just get a bigger gun, especially given the availability of options. So I don't buy extensions any more, I buy the gun in the size I want and with the capacity I desire in a flush fitting magazine.