Ive been meaning to comment on this thread and kept forgetting.
Its common practice to adjust pretravel and overtravel on target and range guns. Besides as a hunting gun i see no other uses that doing this would be an issue, Your gun has a manual safety.
I know Belt-Fed says he used a set screw, I prefer shims as they aren't permanent and can be removed without a trace if i sell the gun.
I started with polishing everything all mirror like, Then set out to adjust the pretravel.
Id say i added 3mm of shim under the trigger where this part in the OP's thread would hit the underside of the trigger also.
I have a JP spring set coming, But have a very light set on it now i been working with.
The gun still has a 3mm trigger pull which is about 2x less than stock, But its more consistent as its already in the process of pulling the hammer back instead of just starting too. You have to watch your trigger system work if you don't know what im talking about.
Now heres where it gets odd. I don't know the range of adjustment this "gadget" setscrew for sell has. But i had to replace my disconnecter spring with a shorter one to allow the disconnecter to not jamb up sitting so high now.
Next issue is the safety, It will NOT fully engage with lots of pretravel taken out as much as i did. Luckily S&W used plastic for the safety lever and you need to grind the flat area down about 1.5mm so it will fully engage when cocked.
I have a spare metal DPS lever if i need to return it to stock.
My gun is a range/target gun and maybe some hunting this fall for tree rats. So AD's don't worry me, I don't do this with my "work" guns like my HD and CCW.
The gun is just as safe as a stock gun imo, Unless slammed on the concrete or dropped 2 stories from a building.
But basically i have the feel and pull of a 2 stage trigger without the costs.
Nice 3mm length pull with no over travel.
Consistent 2lb pressure.
To say the item for sale is dangerous is misinformed.
But the part also isnt just "plug and play" you may need fine tuning on other items.