I read on another forum the5% mix number, too. I believe it is the same mix for '08 also. I haven't seen the total production numbers for '07...not sure they are even available yet. But, if you use '05 (~160,000) and '06 (~165,000) and then assume the '07 numbers are somewhere around 165,000and take 5% of that, you end up with 8250 or so '07 CSs.
Seems like a reasonable guess based on what I've seen at Ford dealers the last two years (Four new CSs for sale at my local dealer yesterday).
Not sure about how to get a build number for a new gen CS.