Installed lots of stone resin trays ( often mx elements) with stick on feet without any problems..try to avoid putting any pressure on the feet during the install...dragging/tilting tray. Level the tray and set the height for the plinth from the finished floor. Seal the edges of the tray back to the substrate with a good quality clear adhesive and leave it to cure.
The plinth kits often come with velcro arms and sticky pads to secure the plinth. The adjustable arms screw to the sticky base plates that adhere to the bottom of the tray. Make sure you orientate the plates when you stick them or the arms won't fit properly