I've used small cardboard 'shims' placed under the black foam on the outside edge,
Small cornflake packet thickness at first, then slightly thicker card (about .5 / .6 mm thick) at the maximum (where both locos were photographed).
So as the train goes around the bend, the track gradually lifts, then eases out again. While of zero actual value in this scale, I feel it adds that little subconscious element that makes it worth doing,,..