hello kjames,
i am left handed as well.
i actually pinch the weapon with the strong thumb and trigger finger keeping the trigger finger straight. rotate the middle, ring and pinky finger on the front strap and use my middle finger to hit the mag release.
i am as quick, or quicker (practice) than anyone else.
interesting thing happened too, being a lefty.
i was inserting the magazine and the index finger of my support hand just happened to wrap around and hit the slide stop on the left side of the gun dropping the slide (idpa slide lock reload).
that is what i now use to drop the slide since the support hand is already in position, i just rotate to a full firing grip after i drop the slide with the support hand.
this is very fast for me and insures the magazine is inserted before the slide stop is engaged.
hope this helps
have a good one man
will s.