My main concern here is the standpipe and trap. The shower trap was 2 feet below the slab underground. Can I keep it here and just extend the standpipe from there or should I move the p-trap up above the slab? If I leave it down there, the standpipe will be pretty long and I think I've read that's a no-no. Moving the p-trap up above the slab would obviously shorten the standpipe length.
Thanks for any direction, fellas!