additional info
I sorta guessed on the hole placement on the guide rod.
I wanted .75" back from the pointy end (thanks for those words BMCM) based on measuring, but did not want to get to close to the end of the dust cover or behind/concealed by the dust cover to ease stabbing of the takedown tool.
another factor to consider was the length of the captured assembly for ease of installation. The spring plug is fitted to the slide and has to be clocked with the flat wire spring installed. I might have to deburr the end of the spring as it only allows rotation in one direction.
One thing I did not figure into my calculations was the placement of the slide on the frame to reinstall the slide stop but I dont think that would mattered to have an exposed guide rod hole.
I also installed a WC Shok Buff and it appears I have enough slide retraction for ejection and feeding to occur.
Captured recoil spring and almost a lined up notch for install of the slide stop.
and slide lock with no real effort
while I know this is not for a Smith.... I hope my direction help someone fit a recoil spring in their piece!!!
take care