On a more analytically conspiratorial note, have you noticed any subtle trend of folks who stayed in the PCUSA forever until they finally gave it up over the homosexual issue, then come to the PCA with all the other baggage that should have been left behind (women's ordination, inter-religion social service affiliations, etc.)?
Warren, you steely-eyed-missile-man of the PB, you! Your observations are spot on about the tendency in all of the breakaway groups from major denoms. My group broke away from the ABC with the proverbial straw breaking the camel's back over homosexual ordination. But, with that minor genetic mutation, they are quite similar to the ABC DNA in most other respects. You put into words what I have observed in my group and suspect will be the case in other breakaway renewal groups from the major mainlines.
Those in the PCA who are recent expats from the PCUSA will likely carry a lot of mainline assumptions, attitudes, and doctrinal views, many of them unconsciously.