If/when a mag extension is available for the R9, try putting one on. That 1/2 inch added to your grip will make a lot of difference in the control you will have over the gun. I don't have one for the R9, but have one on my seecamp and it does wonders to tame that little beast.
For most regular sized guns, we're taught to use the area between the tip of our index finger and first knuckle on the trigger; however if you look at the physics of it and consider the short distance between the grip and trigger -- you can see why there is a problem when trying that same trigger finger position with the smaller gun.
The length of your index finger usually travels parallel to the slide (on a normal size gun). You use the tip of your finger on the trigger and that maintains the stability of your index finger along the side of the slide and the only subsequent movement results in the tip of your finger on the trigger.
But when you try that with the shorten span of the Rorhbaugh, your index finger moves away from the side of the slide and finger tip creates a triangular gap between the slide and trigger (weakening your grip) and resulting in that trigger guard slap.
I insert my trigger finger a little deeper when using the R9 or seecamp.
Here are pics of the two grips -- its a seecamp, but applies to the R9 & demonstrates what I'm trying to say:
You can see I've lost some real estate on the grip of the first picture. Inserting my finger in a little deeper keeps the index finger stable along the side of the slide. I still only use the finger Tip to activate the trigger, it is just closer to the knuckle than a traditionl grip.
I do not experience trigger guard slaps or any pain any more!
ETA: I'm still a novice shooter, and far from having the expertise of many on this forum, but I wanted to share this is what works for me.
