My builder has started putting up roof trusses, which have a raised tie. He's made the birdsmouth to seat them onto the wall plate 70mm deep into the 150mm trusses. I've read that the cut shouldn't be more than one third of the total depth. Does this mean the BCO will fail the roof, or will I get away with it? If it's no good, will I be able to strengthen them in some way to save them?