Hi Guys,
Sorry I haven't given an update. I've been going slightly nuts trying to get ready for a presentation next weekend.
I've had the firing pin spring compressed for several days, and it looks like that did the trick! I haven't had a chance to get to the range, but the slide locks up much better now and the firing pin consistently leaves solid strikes on empty cases. I should have the right balance between the recoil & firing pin springs now, and I think that reducing the striking surface of the firing pin gives you a lot more margin of error when trying to get the spring tensions right. Thanks a lot for all the suggestions!
P.S.
For all those considering the Ciener kit, I have to admit that I'm not very happy with it in general even though it seems to be working now. I think it has a very limited life; steel just tears the hell out of aluminum. My factory slide lock has already carved out a millimeter or so of the aluminum slide, just from (manually) locking the slide back. Also, the aluminum recoil spring guide is getting really chewed up by the locking lug on the barrel.