Carbonating half of a keg

I have a 5 gallon batch that is about to finish. I am entering it into a homebrew competition at the end of the month. The homebrew competition requires that the beer be bottled (3 bottles for the competition). The rest I want to keg for my own enjoyment. If I bottled 2.5 gallons of it and keg the other 2.5 gallons will force carbonating work the same. When the keg is half filled there is much more headspace obviously...can I still just set it to 30psi and leave overnight and it will be carbonated the same as if it were full? Anyone thats ever carbonated a keg that wasn't full please help me out if you can. Thanks.

It works the same as usual or at least I didn't notice a difference between half a batch and a whole one.

it's exactly the same. Put it on pressure, and give it some time. Same pressure as you'd use for a full keg, and the same amount of time - whether you're using the 'set and forget' method, or putting it under high pressure for a shorter time and then dropping it back down. Nothing is any different.

About the only thing I'd do differently is to purge the headspace twice, before letting it carbonate.

thanks for all the comments....