the recommended way to apply silicone sealant around the bath is to fill the
bath with water first so it sinks a little - that way you don't stress the
sealant when the bath is filled.
However maximum stress is when the bath is filled to the overflow with one
(or if you are lucky) two people in it.
[Lit candles for effect are considered of negligible additional weight.]
Therefore logically you should apply silicone sealant with the bath filled
and at least one, preferably two (British Standard) people in it.
(1) I am not sure the guy who fitted the new bath in our bathroom a few
years back knew the correct way to do things.
(2) If this is encompassed by future building regs. I am retraining as a
plumber (but not engaging an assistant).
(3) Whatever, I fit my own baths from now on!
P.S. perhaps I should cut down on shower time?