there's nothing as "hidden partition".
Ustealth is hiding the full drive, not partitions.

Actually, it's corrupting/editing the partition table signature to prevent the WiiU from seeing a table and asking to format the drive (to delete the table).
if you want a WiiU format, it will format the partition table (where you define up to 4 partitions) and therefore you can't have multiple partition on that drive.


There is still a way to do it, but it had NEVER been tested (only theorized?), being too complicated: there's a way to "physically" (firmware based) restrict the HDD size.
- format the drive to GPT, the partition table will be located at sector 0 AND a copy at end sector.
- make 2 partitions, format the second one to FAT32, keep the first one not formatted to skip it.
- make the drive smaller using special tools which talk to HDD internal firmware settings. resize to hide the second partition.
- format the HDD to WiiU format. it will see a table at sector 0 and will format it without a partition table up to the end of the (fake) HDD size.
- resize the drive back to full physical size to unhide partition 2 and GPT table backup at the end

- update ALL homebrew to read partition table from end of drive instead of sector 0
- update ALL homebrew to read GPT instead of MBR
- pray the tool work for your HDD and you don't lose data, or "brick" your hdd in the process.
- hope your OS will look at the end table too, or it will ask to format the hdd to recreate the table at sector 0 and delete your wiiu partition
I don't think a lot of tool/app/OS are written to look at the backup table. probably none. (I don't even know if partition managers are doing it properly either)