never had an issue with finger falling into trigger guard. when i draw my index finger goes along the frame right below the slide and never goes into the trigger guard. it comes down to personal preference. i have carried in my serpa for 13+ months with no issues. i am comfortable with it. and i have practiced alot. my LGS range made me do 15-20 "dry" runs before allowing me to pull from my holster and fire on their range. they said typically we dont allow drawing from a serpa but you seem to have it down to where you wont mess around and put a round through your leg.
try alot of holsters, find what you like. ask the LGS to supply a unloaded display model of your firearm, never pull out your firearm in a store. thats about all i can add to this one at this time
When drawing my finger always goes straight outwards and ends up just forward of the ejection port. But then again that's just the way I was taught. I imagine with the location of the release button that some people have shot themselves, but it seems to me that if I let my finger slide on the draw that it would correct and land where it.usually does.
I apologize for the mangled hand. It broke a few years ago dispatching a couple high schoolers that called themselves a gang and my doctor was way past retirement age.