a 11/6 will be fine,if anything your going to get more speed out of the 6pitch than a 5pitch,it should't make that much difference for you though.
when I first started out with my NEXTAR I busted 3or4 of those props so I got a bunch since they were cheap 2$ea. now I use them for my .46 sport plane they work pretty good.
I don't think I busted even one more after I bought all those of course.
the NEXTAR is getting a over haul right now,OS 61,new covering, and floats, can't wait for the refirb.