Scaling will probably be a good idea.
Another factor will be if your 'ship' can actually, 'slide' over the 'hill' - if it is too steep, it won't coz of the gravity being applied - you could try amending your gravity. If this works then just amend gravity at the point of going up the hill. You can also test this by changing the gradient of the hill - to see how this works with the gravity applied - experiment with this.
EDIT: your problem could be a combination of this and the scaling.
Another factor will be if your 'ship' can actually, 'slide' over the 'hill' - if it is too steep, it won't coz of the gravity being applied - you could try amending your gravity. If this works then just amend gravity at the point of going up the hill. You can also test this by changing the gradient of the hill - to see how this works with the gravity applied - experiment with this.
EDIT: your problem could be a combination of this and the scaling.