I'm new here and would first like to thank all who contributed to this thread and took the time to make this information available to others.
After reading the whole thing, I decided to mod my iPod video 5.5 80gb by using Tarkan's adapter and a Hama 128GB SDXC card, which seemed to me the most straightforward solution.
This was not the case however. After installing the adapter and formatting the card, I managed to reset the ipod and get itunes to recognise it. The problems started when i began transferring music to the ipod. I first tried loading a whole 80gb in one session and the ipod froze almost immediately, stuck on the "do not disconnect" screen. After a couple of failed attempts i tried to reduce the size of the load and it seems to me that transferring a little under 1gb works most of the time, albeit not always, since i still get stuck on the same screen and have to do a hard reset of the ipod.
I believe i have read about someone encountering a similar problem, but going through the whole thread again sounds like a nightmare to me.
Do you have any idea of what might be happening? Do you think it could be the SD card's fault?
I also tried installing RockBox, but i get the same problem when transferring files to the ipod, among other things (installation was a dreadful process, could not get it done on my Mac, had to borrow a PC from a friend).
Sorry for coming back to perhaps already solved problems, any help would be appreciated!