Are they under or over the muscle?
Over the muscle, no issue whatsoever.
Under the muscle, if you are concerned, just for your own mental well-being, go back to your surgeon.
That being said, I think they are designed and tested in such a way to take a HUGE amount of pressure.
You still have fat on your breasts which will fluctuate.
I do know one FBBer who swears she flattened hers out by training chest heavy, hers were under the muscle.