Well then, maybe this information may persuade you to consider not doing so, as it is a grip configuration that is counter-productive to pistol grip strength and firearm control.
IF you need to get to the punch line, then start at the 3 min mark regarding grip management; Bill Rogers explains the grip here:
https://www.dropbox.com/s/xxklp1sz2t1v0bv/Bill Rogers Explains Dominant Eye Grip & Stance.mp4?dl=0
By opening up your grip to place either your support hand index / or social (middle) finger on the front of the trigger guard you are sacrificing about 25-35% of your grip strength which is not good for recoil management.
A good analogy of single hand grip strength about a pistol grip is that of a carabiner. A climbing carabiner
is rated for strength in its longitudinal and cross axis as well as that with its gate open. A typical carabiner
is rated at 24kN along its long axis however with its gate open the strength is reduced to 7 kN. Such
is the case when one doesn’t reconfigure their one-hand shooting group from typical a “high-thumb” position
(brief case grip) that affords room for the support hand with a 2-hand shooting grip, to one that opposes
the thumb with their middle finger (power grip) that closes the anatomical “link” of the hand grip.
Here are just few of pistols (HKP30, HKVP9, Walther PPQ M2) with square trigger guards, I continue to be amazed that mfg. construct them when its well known some will try to use them in that fashion, despite the knowledge to the contrary.
