From reading the first post describing where the blister is forming it sounds like you are riding the trigger really low and it's pinching your finger between the trigger and guard on the return. Does that tie in with where the blister is forming?
I wear large or extra large size gloves depending on the fit. But mostly XL's. So my hands and fingers are not small either. I find that my trigger finger fits nicely in the stock curvature. And with a good high placement of my hands to let the gun sit really low in my grip my trigger finger sits neatly on the trigger's curvature. Perhaps your grip method is slipping a tad and allowing your trigger finger to ride lower on the trigger and promote dragging and pinching on the guard? If this is what is happening then fitting a new flatter trigger won't help. It's more about your finger position on the trigger. Holding low on any trigger will still promote pinching your finger between the trigger and the frame due to the trigger on the Shadow (and all CZ's) being a top swing style.
One of the better videos on grip that really does a good job of showing and explaining the support hand wrist cant to get the gun really deep in our grips is Travis Haley on Gun Grip. Perhaps try your usual grip first and do a little dry firing and see if you're tending to let your trigger finger get too low. Then look at the video and work your grip method to really get the gun deep down into your strong hand. The web of your hand should be stretched fairly tight into the upper "beavertail" curve. And adding your support hand on the other side should not tend to push your strong hand grip out of position and down the grip area at all. That'll keep your trigger finger up higher on the trigger where it can get a different blister from the burrs around the travel screw hole or where the trigger goes up into the slot and the scissor action gives you a different sort of blisterIf/when you get a blister from those higher up features find the happy middle ground in between.
Its definitely not pinching between trigger and guard. Its almost as if my finger is naturally hitting g a poor angle on the trigger itself even though my finger pad is centered in the middle of the trjgger, if that makes sense.