Originally posted by WhamyKaBlamy:

You can make signs and a kind of lattice to keep your chests in, so you can put your signs above it.

On the left is how we do it. I know it's not bigger chests, but it makes life easier.
https://steamcommunity.com/sharedfiles/filedetails/?id=2520959350

I do something similar, but I put my chests in endwise. You can put in chests almost touching and get nearly 3 times as many in only a bit more space.