Just bought a used STI 2011 with a SVI trigger with long flat insert. The trigger is way too long for me so I need to buy a new insert. I haven't found a sizing guide anywhere and I don't want to buy a bunch of different inserts trying to find one that fits. The measurement between the tip of my index finger and my wrist is 7". If I go with another flat trigger insert, should I go with a short or medium?