painzstaking

Hmm. It makes sense if there were some kind of juncture between the /s/ and the /t/, that the voicing would occur (i.e., /s/ > [z]), as is usual in such cases. It seems the choices are:

a. pain + staking, /pejn#stejkIN/
b. pains + taking, /pejnz#tejkIN/
c. pains + staking, /pejnz#stejkIN/

In casual speech, I think I pronounce it (a). As per Faldonem, YMMV.

Ceci n'est pas un seing.