I was one of two non-121 guys in my class. It was harder for us two than the other guys/gals in the class that were coming from regionals. They were basically just getting a different type while we were also being indoctrinated into the 121 world. Both of us had extensive 91, 135, and 91k experience and multiple types but it was still harder and it is a fact that the non-121 guys do have a higher failure rate. It's not impossible but plan to be studying a bit more.