I don't have this weapon but if I did I would shoot it for 3 or 4 months regularly without the pinkie extension exclusively. After that time I would imagine I would have adapted to the grip and would not miss the extension.
If you apply the extension early you will miss it no matter what.
By in large the human body (and mind) is highly adaptable. I would not compromise the concealability until I have exhausted my efforts to adapt to the weapon without the grip extension.