Hiya,
Not sure what the issue is with the back plate. But that is a lot of prop for a .46 LA. I run a 11X5 on my AX which has much more power than an LA.
Try a 10X6, maybe 10X7.

Some wooden props do have the blade reach back slightly behind the hub. These props aren't intended to be used with spinners, but with conical spinner nuts.