You won't go wrong with adding in empty boxes. Maybe I made it up but I swear I remember seeing on CI, CBID or Famous where they would send you a random assortment of empty boxes for a certain price. I can't seem to find it, maybe someone else here know what I'm talking about.

My only other suggestion would be to make sure you keep it out of sunlight since it's clear. The sunlight will crank up the temp in the container and not only will you have temp swings but RH swings as well as it heats and cools.