Expanded Storage is a mod that will increase the capacity of a single chest by upgrading various tiers from iron to obsidian. This can subsequently expand the storage of double chests as well.
You can craft individual chest tiers with the key ingredients associated to that type of chest. But it needs to be done by crafting the previous tier first and continuing up until obsidian. The storage space ranges from 27 to 108 stacks. Plus when you get to obsidian, the chests become blast resistant.
Or you can upgrade chests with upgrade blocks. They have to be crafted in order as well but you can jump several tiers with one upgrade to an already full chest.
And this mod also gives a couple of variations on double chests by allowing vertical and alternate horizontal orientations.
This mod requires an additional API found here.DownloadForumInstall Guide