Here here on the CVF article Jeff. Harriers launching from an Invincible don't use the whole deck length, they typically begin their takeoff roll from about halfway to two thirds of the distance from the ski jump, allowing up to four Harriers to be 'spotted' ready for launch simltaneously. Given the necessary separation between the aircraft, the first to launch must start it's run from the halfway position. The point of the ski jump is that half the takeoff run is completed AFTER the harrier leaves the end of the ramp. Cmdr Doug Taylor who invented the concept back in the early seventies originally called it 'The Runway in the Sky' specifically because after leaving the ramp the aircraft will not have reached wingborne flying speed (normal ramp exit speed is about 80 knots) but is beginning to generate lift from it's wings. This is added to the upward momentum imparted by the ramp, similar to going over a hump backed bridge in a car, but unlike a car the aircraft is subject to continued acceleration and thus reaches fully wingborne flight before it reaches the apogee of it's trajectory, at which point it begins flying conventionally. The upward trajectory imparted by the ramp has the added virtue of lifting the aircraft away from the level of the deck so that if there is an emergency the pilot has more time to react than with the flat trajectory of a catapult launch, so it improves pilot safety.
The DDHs have ample deck space for spotting two or three aircraft for launch, as this 'artists impression' shows:
fitting a bow ski jump as shown would be a straight forward proposition as it is a simple steel structure (with no moving parts!)and in the position shown would mean no loss of helo landing spots. A simple modification which could be applied in a few months if required.
ff jeff are you going to add a CVF article since now its thought main gate as that was the reason why it wasn't added the first time 