For future reference there is no need to rack into a secondary unless it will be ageing for months or you are adding fruit. It's not necessary when adding fruit but it's less problematic as the renewed fermentation caused by the fruit will fill headspace with co2. For long term ageing you do want to fill to neck.
In your case there is an increased possibility of noticeable oxidation occurring faster, with a likely symptom of reduced hop aroma/flavor.
The solution: drink it fast!
The reason I went for the six gallon carboy is because I added caramelized figs. In a previous batch adding figs, I racked to a five gallon secondary and there wasn't enough room once the figs began to ferment.