I was inspired by another user who did this on their classic so here is my Mint and custom 128GB iFlash Solo (running 128gb Micro SD) iPod Classic 5th Gen with this
Create Your Own iPod Video 5th & 5.5 Enhanced Tarkan iFlash SD Card 20 – Elite Obsolete Electronics
iPod 4th generation or Photo hard drive replacement by micro SD card - iFixit Repair Guide