People- get the need for thrust reversers off your mind! All landing performance is calculated without including any thrust reverse. On these really big engines, it is quite common to find the mechanism doesn't travel correctly and reverse won't apply. They are also not very efficient at actually reverse thrusting. Nice to have when conditions are pretty horrible, but any aeroplane can land perfectly satisfactorily without applying reverse thrust at all! It is a perfectly sensible decision for Airboos not to install it in the outboards- FOD ingestion and it is a big engine to have all that reverse so far from the centreline- I recall a 747 taking a swim in the Pacific for this reason.