Re: One piece shower was installed incorrectly
If you can gain access to the underside of the pan through an adjoining wall, then you can mix up a batch of stiff mortar and pack it under the pan. You want the mortar to be the consistency of wet sand or slightly wetter, just enough so that it stays clumped together and doesn't sag when left alone.
I personally am not a fan of fiberglass units. A pan only is one thing, but a full enclosure is just too cheap looking and feeling for me. Since there are no leaks or problems with the shower/pan, then there is no rush to replace it unless you would prefer having tile.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!