Has anyone swapped out to a lighter mainspring ala` the Beretta 92 in order to acquire a light, smoother trigger pull? If so, how much did you drop down & still retain reliability?

Thanks in advance.

Yup!

92FS Compact Railed,, got the Wilson Combat Action Tune Kit. The 12lb spring in there gave an extremely light pull, and gave me 2 failures to fire in 600 rounds. For a competition or range gun I would have been fine with that, but it is a defensive rig, so I upped it to the 14lb spring. So far (750-1000rds), I've had no failures, and the trigger is just beautifully smooth. I also installed the elite hammer, though I haven't noticed any major difference and will likely switch back to the Beretta skeletonized for looks. The WC Steel Short-Reach trigger also makes a noticeable improvement, and is highly recommended.

Overall, the parts I have into the gun and would recommend to make it even smoother and nicer to shoot:

WC Short Reach Trigger
WC Fluted Guide Rod + Flat Recoil Spring
Shok-Buff buffer (can get with the guide rod and spring)
WC 14# Spring
Beretta Skeletonized Hammer

If you have any questions about it, feel free to ask. I'll see if I can get a weight on the trigger pull here soon. If you're in north Texas, HMU.

Update: actually got my pull measured today. DA came in at about 9lb 5oz, SA showed a pull of 4lb 2.8oz, but was breaking at 3lb 14oz.

I have a Wolfe 10lb spring in my P2000SK. I don't know exactly how much it lowered the DA pull but it was enough. I have only fired a few hundred mixed rounds through it but it has fired everything I've run through it.