Don't know if it helps, but this is what I did to my S70...no frame or slide modifications:
www.ar15.com/forums/topic.html?b=5&f=49&t=278893rd post down is what I did.
I could have saved a lot of time had I just skipped the whole ejector part, but that's what makes it all fun. I learned a lot working on this gun, and I didn't make a single change to it that I cannot undo.
Now, if you are hard-set on sending it off to a smith..well, there's no end to stuff they can do. Me, I'm happy with a looser gun than the customs out these days; yes, my slide moves a fraction on both horizontal and vertical planes. It's also slicker than snot running downhill on ice, and I can still reliably hit COM on a police target at 50 feet without concentrating on it, over and over. It's no race gun, but for it's intended purpose as a reliable defensive weapon...well, it's what I carry with me, so I obviously trust it, and the work I did to it.