The smaller the drybox the harder it is to stay dry. Here's what Pelican recomends: Before you thrown something expensive in the box test it out. Put a piece of dry paper inside the box, fill up you kiten sink and hold it under water. Wipe off the outside and check the paper inside. If it's wet return it and try another box.
The little boxes only take a tiny gap to fail, but they have the smallest compression seal as well. They will have more failures than the larger cases, w/ larger O-rings. And, never over fill the box. If it is tough to close in any way, it will not stay dry.
I love to dance, but who needs the music- It throws me off.