Yup I remember reading in a post that someone found a way to upgrade their axim x50v using X51v rom images and were going to try A12 on their X50v using the same method. Just a matter of finding it for you... never tried it myself though.
however I recommend trying these hacks on a X50v with win5 because Ive had mine running with them for a few months with zero problems and haven`t had to even soft reset, it`s got my Ax running at Win2003 speeds.
http://www.aximsite.com/boards/showthread.php?t=125990
EDIT: ok managed to hunt it down
http://www.aximsite.com/boards/showp...&postcount=164