predictions of straight 5as doesn't seem to hold any sway in some authorities either.
I'm certainly aware of authorities where very strict appeal panels appear to be rejecting curriculum-based evidence out of hand on the grounds that it is completely unrelated to reasoning tests as used in the 11+. Seems extreme to me, but I do always recommend the inclusion of some non-curricular academic evidence (e.g. CATs) wherever possible.
The majority of panels will probably take KS2 predictions into account, but remember that three level 5s are only a starting point for an academic case .....