Guys, i just discovered something amazing!
You know when you're adding a new fingerprint to the list and you have to swipe the scanner 8 times? Well, nobody said it had to be that same finger, all eight times.
I was able to register all my fingers because with this method i have 24 (3 x 8) places to store fingerprints.
I've seen posts where a dude asked if there was a mod to register more than 3 prints, well it was just that easy!
Can't say if it affects the accuracy of recognition as i found this only 5 minutes ago but so far it seems fine with all fingers.