3D Tileset photogrammetry model overlap with terrain

Hello community. I have 3D tileset as photogrammetry model placed on Cesium Terrain, see sandcastle here. Unfortunately tileset has areas which are below terrain and thus they are not visible.
Question 1: Is there any setting to dissable terrain in those areas or prefer tileset over terrain or something to actually see tileset data?
Question 2: If I would like to use only WGS84 ellipsoid as terrain (flat), I would have to set height of the tileset lower because it floats in air. I know there is sandcastle demo which shows code for function to set its height but I want to set it as fixed in code without button,
Question 3: I would like to increase cachebytes and maximumCacheOverflowBytes but dont know how to implement it in my code as documentation is not clear for me :face_with_monocle: and coulnd find any example codes that implement them.
Appreciate any help in advance :slightly_smiling_face:

Update: I found answer to Question 1. I can use use points with clipping planes to cut terrain.
The remaining questions still need answer.