I have taken several kydex holsters and reformed them to another firearm that I bought new...
If you were to change the retention of your holster you would need to do the following (and no, I am not responsible for your actions!:tongueout
using a heat gun gently wave the heat gun over both the trigger guard and the ejection port areas. I would not get closer than about 6-8".
When you see the kydex molding slightly deform...STOP!
Using a gloved hand place pressure on the trigger guard area and then into the ejection port.
Using a fan, cool both of these areas and check for retention. If the ejection port area is too tightly molded you will have to bring out the heat gun again to soften it slightly.
Obviously you will have your gun in the holster during all of this work...
Again, this works for me, but YMMV.... :wavey: