I ordered two of the +0 competition mag extensions from HKParts.net. I like them, chose them over the shaped billet finger rest version. It gives enough purchase for the pinky to rest on the mag and full use of my hand for control of the weapon.
ETA: Just returned from a night shooting class with the P30sk. As mentioned above, the two mags with the +0 extension were controllable and accurate. The third mag with the stock baseplate did not give any purchase to the pinky. As a result, I missed multiple shots during drills.