Well there you go Rev, after three pages of discussion over how to hang your brackets, we have some consensus if all else fails.
Screw and plug some batten on the wall, (batten is a thin strip of solid wood around (40 x 15mm ish, wider than the bracket anyway). Use something around twice the length of the bracket, securing the batten "quite" near its ends, that will reduce the load on the fixings and therefore the risk of "pull out". Then screw the brackets onto the batten.
If it still pulls out, use the frame fixings to further secure the batten.
Otherwise leave it outside.