Make Custom Structure Fit Terrain without Trees Clipping and Buildings floating on Water

After testing my jigsaw structure out on a flat world, I've generated a default world with the datapack. I've got "project_start_to_heightmap" set to WORLD SURFACE WG, and "terrain_adaptation" set to beard_thin. It's looking natural enough, but how do I keep trees from clipping into the buildings, or buildings from floating on the water surface?