Nice looking box Chris.

For those larger end grain hollowing/hogging wood endeavors a straight boring bar is my tools of choice. The boring bar is cheap and easy to make with tools you probably already have.

Check out this link for the bits:

http://www.wttool.com/c/22180005p

and this one for drill rod:

http://www.wttool.com/c/07000005p

Personally, I use 5/8 drill rod (cut the 36" in half and make two) and 1/4 x 1/4 x 2 1/2 HSS bits to make mine. I drill a hole in the end of the drill rod using my lathe and a jacobs chuck in the tailstock. Then I use CA glue to hold the bit in place leaving only half of the bit showing. If I need to change the bit, I use a propane torch to remove it. Make the handle out of wood and you're ready to go. You can even put a curve in the end or set the bit in at a 45 degree angle for those hard to reach places in a hollow form. Two nice heavy tools for $12.26.