Yes. There is a primo passagio and a secondo passagio.
Usually, if you have to make adjustments around C4, you will have to again adjust around E, F, F# or G4. It is not unusual for someone to have to work at stretching chest voice for quite a long time before they can remain in chest voice until C5.
If you're already making it to C5 before having to go to head voice, consider yourself to be fortunate. A lot of others would probably like to trade voices with you.
: ^ )
If you are having to go to head voice at A4 (5th fret, 1st string) then that is your secondo passagio. If you have to shift, it's a passagio.
So what is it you're doing at C5 (8th fret, 1st string)? Another shift, because you're already in head voice, if I understand you correctly? If so, then you are shifting from head voice into exactly what? A thinner head voice at C5?
You may, of course, be gradually mixing through any of these regions, in which case it's like a giant, gradual passagio. Most people start out shifting in steps, and eventually smooth the whole thing into a gradual shading from chest into head.
By the way, @musicman, you're quoting Ken in the KTVA volumes, so I'm wondering if you are a KTVA student?
You are listed here as a "Member". If you have purchased a KTVA Volume or Bundle, then you can request to have your forums status upgraded, which gives you access to a lot more KTVA information. There are students-only sections of questions and answers, a lot more instructional videos, and more.
So if you are a student and want to upgrade, then please copy and paste into an email to [email protected] a copy of your purchase receipt(s). Ask for a forums upgrade.