Springy shower tray

[ComicePears]

The shower tray in our shower cubicle (installed by previous owners) is slightly bouncy, and causes the silicone around the sides of the cubicle to stretch and leak every couple of years. We usually get someone to redo the silicone when this happens.

Does anyone know if there's anything that can be done to stabilise it, short of removing the whole thing and starting again? We asked a plumber for advice recently and he suggested adding some kind of filler (foam?) by cutting a temporary hole in the ceiling of the floor below - sounds kind of drastic, does this sound like the standard solution to this problem ?

Id just get a new tray and have it fitted properly

Stick a piece of carpet in the bottom and fill it full of heavy stuff at t
leat the weight of the heaviest occupant bags of sand are good when you re do the silicone around the edge, once dry remove weight and the joint is now in compression so won't crack the silicone.
The issue is the area for the shower tray should ideally have a supporting frame to hold the shower tray, that's the real best fix.
The foam might cause more damage as you cant control the expansion rate