A Staff.TimeSignature problem (for me)

[Robert Blackstone]

Dear all, 

Presently I'm transcribing an early seventeenth century cantata “per una voce 
solo”. Two staves, one voice each (Vocal and Bass).
Also two sections, Sinfonia prima and seconda.
As for TimeSignatures, the first part of the Sinfonia prima starts with C and 
when the singer enters it becomes, after a double barline, C barré.
Again, after a double barline, Sinfonia seconda starts with C.

In the course of this work the \time often changes: Already in  the first three 
bars it is 8/4, then 4/4, again 8/4 etc., up to 12/4 and 16/4.
It is simple to make these changed Time.Signatures invisible. 
But my problem is in the first bar of the three sections: How do I get C and C 
barré at the beginng of these sections?

Thanks in advance for any advice.

Best regards,

Robert Blackstone