Bulk aging: Air space after racking

Cider
1

This is the first time I’ve aged cider in a carboy for longer than a month. I’ve made a few batches over the years but always but them in bombers after a few weeks. My concern is the large space at the top of my carboy. I tried to blow out the air with CO2, but I’m still concerned I’ll end up with vinegar. Should I be worried? I’m planning to rack this stuff a few more times before bottling and I assume there will be a small amount lost each time.

Thanks!

2

I primary in plastic, so I can start with a big enough batch to fill my carboy and a 1gal glass jug when racking to secondary and then use the 1gal jug for “topping off” when it comes time to rack again.
You could also use clear glass beads to “top off”.