Romeo Mike wrote "air in the headspace...if there is a lot of it, bad for
the wine?"

Romeo - YES! The air will oxidize wine...regardless of wine pH and proper
SO2 level, exposure to air will ruin your wine. Leave no more than an 1/2
to 1 inch space between the wine and air lock stopper.

BTW, if you hold your beer in a secondary keeping the same small headspace
will result in better and less oxidized beer.

Bill Frazier
Olathe, Kansas USA