I wondered if I could make just half a box?
I was thinking to measure accurately and just use 2 eggs?
Has anyone tried this?

Funny, I was just thinking about this the other day. I would like to know the answer, too!

Sure, been there, done that mamy times
I have a scale and am able to weight out my mix. Since I use only 2 whole eggs per mix anyway one egg and 2/3C water will finish up the batter.

Why? I store leftover batter in the frig. I've even put the 1/2 leftover box of batter in a greased 6" square pan, froze it, and took it from freezer to oven with no problem. Or I go ahead and bake a 6" square, then cut it in squares for my samplings.

I actually eyeball it into 3rds since that is easier to deal with than spliting an egg in half...LOL! All my quarter sheets and 2 layer 8" rounds take exactly 1 1/3 box of a DH cake mix. It is the perfect amount to get just the right height.