Hey, thanks for jumping in on our product release and bringing up some interesting points:
Our engineers extensively tested different designs and capacities for the Samson magazine extension, and since our goal was to create a product specifically for a carry gun it had to be reliable 100% of the time. Our testing showed that in order to use the factory magazine spring after repeated compression cycles and using a variety of ammunition types, that the +1 configuration on the 8rd magazine fit the performance range we were seeking, and is the equivalent of the +2 products used with the 7rd mag.
We also supply a new spring seat/base plate retainer to ensure proper spring alignment using the factory spring as we found the factory retainer could shift and impede performance. This retainer allows for factory-style disassembly of the magazine without any screws or additional hardware.
There are other extensions on the market, however we feel that ours meets the needs specific to CCW/defensive carry and is reflected in the profile of the extension. Shooters can clear any Type 3 (double feed) stoppages more easily with the finger cuts on the sides, or with one hand using the notch on the front. Experienced shooters know that rapidly clearing a Type 3 requires the shooter to manually rip the mag out of the gun with some force. With wet, cold or bloody hands the scallops give the extra purchase you may need under stress.
The profile also keeps the mag from hanging up on your hand when performing rapid reloads. Factory Shield mags hang up and force you to shift your firing grip to clear.
Also, the Samson magazine extension is designed to work with the Samson magazine well if one chooses to use one. The magwell adds a tremendous amount of control and is especially beneficial to shooters with large hands.
(My personal favorite combination is the 7rd mag with the +1 extension, which gives me a full grip and an extra round of capacity)
Thanks again, and stay safe!