USB stick or HDD to expand images?

I would like to know the maximum size of a USB stick for installing images.

I tried with a 512 GB one, but I couldn't get it recognised on Egami 11 and Opena ATV.7.5.1

on an Ultimo 4K.

I welcome your advice.

I tried all the procedures provided by Egami and Open ATV, but without any results. Now I have inserted a 256 GB USB stick and followed the same procedures, and it is recognised.

I have solved the problem!