Cloud Storage adds a really creative take on modular storage that I use quite often, unfortunately Cloud Storage doesn't allow for Sophisticated Storages to be attached with Balloons and added to a Cloud Chest.

I'd really appreciate some sort of addition that allows for your storages to be used. Cloud Storage allows for most other mod's chests to be used. Here is their GitHub!

https://github.com/AlexModGuy/CloudStorage

From the first look it seems you need to ask them to add compat because it looks like they only take number of slots from the given storage and add that to a huge cloud chest. Have you tried speaking to them about adding compat with modded storages in general?

I haven't had issues with other storage mods so far which is why I opened an issue here first. I'll gladly open an issue over on their github though, I guess I hadn't thought about cloud storage adding some sort of fix for this instead.

Probably would make more sense for them to add some sort of option to add extra storage blocks to the mod, maybe via a config or datapacks.