shower riser kit

Hi, I recently bought a Mira flight safe tray 1000x800 mm that needs to be raised. Are Mira riser kits sturdy or wooden frames are considered to be more solid?

Am I correct in thinking that the plinth of a riser kit should rest over the floor tiles i.e. the bottom of the plinth is set to the finished floor height, with the end of the tile run just tucking underneath? If the above is the case, then I assume that the edge of the tile stops before the...