I ferment in 10 gallon cornie kegs as well. When I transfer from fermentor to serving keg, I run the first 12 or 16 ounces into a sanitized container before redirecting the flow to the serving keg. This takes care of the initial yeast/trub pick up. I don't think you lose any more beer this way than you would with a shortened dip tube.
You might run into a bit of an issue if you let a lot of trub into the fermentor and you crash cool before transfer (in that you might have to really jack up the pressure to push the initial yeast/trub pick up out through the dip tube).