ak 4.21 savefiles on AKAIO 1.6RC1

help needed!!
first i had the official AK 4.21 firmware, but now I use AKAIO 1.6RC1.
the problem is, I can't use the savefiles from AK 4.21 on AKAIO 1.6RCI!
does someone know how to use AK savefiles on AKAIO??ps: I'm dutch