How much head space on 2ndary?

I have recently made a batch of Java Stout, which I put to the 5 gallon mark on the bucket like always in the primary. The recipe calls for 48 0z of Coffee to be added to the secondary.

So when I racked the secondary last night, I notices very little head space. The surface diameter of the top of the beer is about 4-5".

So I was wondering, can this cause a problem? usually the surface area is the maximum width of the carboy. So I was wondering if it needs that much exposure for oxygen or anything like that. Just never had a carboy this full.

Thanks a billion beers guys

Well I don't know for sure, but the amount of sugar/fermentables in coffee - just brewed, not modified by milk/sugar/creamer, etc... should be pretty low.

I doubt you will get much action on it, although with only 4-5 inches, it will all be condensed to that area rather than like 15 inches of surface area of a bucket, or about 1/10th the area... Still I think you'd be fine

Ideally, you actually want very little headspace in secondary, like only an inch or two from the top. Some may even say that the headspace that you have is too much. Personally I think you will be ok, as I have had over a gallon of headspace in secondaries without issues.

You may also find that most people aren't using secondaries anymore, except for certain circumstances such as long term aging and for severe filtering/clearing. If it were my beer, I may have ignored the directions and added the coffee to the primary a week or so after fermentation had stopped, then bottle/keg after the required amount of coffee aging in primary.