IMHO; 17lb is too weak, and slams the slide stop.
What do you mean by "slide stop"? Are you talking about the slide release, or the "slide stop" that you must depress to take the slide off of the frame when field stripping?
Either way, how would a weak recoil spring have a negative effect on this slide stop?
I found that the DPM does not throw the brass like the standard spring but I don't recall what the total combined spring rate is.
If it doesn't sling the brass as far, then this must mean that the slide is not moving to the rear as fast as it is with the stock spring installed when the brass hits the ejector. In effect, this means that this recoil reduction guide rod performs the same function as a heavier recoil spring, at least in this last section of travel.
For reliability reasons, I'd rather go with a recoil spring on the lighter side than on the heavier side, as a lighter recoil spring is more likely to function reliably with weak loads, a weak grip, and/or shooting in awkward positions, all of which are possibilities in a defensive encounter.
There is a limit to how light you would want to go though. Keep in mind that there is a striker spring in the pistol that pushes the slide in the opposite direction as the slide is returning to battery. This is one reason why recoil springs for striker fired pistols are generally heavier than recoil springs for hammer fired pistols. Also keep in mind that a lighter recoil spring means that the slide will move faster to the rear, and all of the springs need to keep up. The mag springs need to push the bullet in the upward direction fast enough so that the slide does not "outrun" the cartridge when feeding, and the extractor and extractor spring will be getting more of a workout. Lighter recoil springs should increase frame battering in the rearward direction of slide travel as well.
The manufacturers put these springs with these spring rates in there for a reason, and they tuned each spring rate to function with one another. I'd rather leave the pistol stock. In my opinion, there are far too many people on this forum that feel otherwise, especially in regards to defensive pistols. What, exactly, are you guys trying to gain here, and what exactly are you using these pistols for, if you don't mind me asking?