I'm not 100% but it's been my understanding that you'd be better off with a b18c1..

b18c1 = less horses off the bat (170), but can handle a lot more boost in the long run.

b18c5 = more horses off the bat (190), but handles less boost stability..


I don't know anything about the axls, and i'm sure someone'll either say i'm on the right track, or correct my statement shortly, good luck either way.