My local CAA allows thrust reverse to be used for ALD calculations on wet/contaminated runways but still LDA has to be 67% longer than ALD at destination or 42% at alternate. 560 or 30 ft on 4927ft long runway doesn't sound like 67% margin to me but then I'm no expert on FARs. Perhaps FAA allows lesser margins. Anyone on the other side of the pond care to comment?