Well, going by the official RO rules, unless they changed it without my knowing about it. -.-
You can technically turn Sin X if you weren't originally a Sin. Only they would call it "high assassin" instead of "Assassin Cross" because you don't get all the bonuses of a Sin X. I'm certain you do /did take a hit to you HP / Sp...normally transcendeds get +30% max HP and SP, while cross-classing you didnt' get this bonus. You might lose the stat bonus too, didn't hear about that though.
Might have changed since I last heard though- there seems to be several changes that happened without my hearing about it. x.o
![[Image: 180da8wb2.gif]](http://img142.imageshack.us/img142/5898/180da8wb2.gif)