Rear discharge Vs Center Discharge with pipe to rear.

Only con I can see is a lot of the time when a rear is requested its usually because theres an incline or whatever you want to call it, So if you backed down the bay with a belly unload you might leave a heel

 

Sometimes the customer wants to use their permanent hose which may not reach unload port in center of trailer.

 

Matlack built some conicals 30/70 making the outlet closer to the pump.

That would leave a heel in a pit where a rear valve, non-conical barrel would not; wouldn't matter on level ground.

Most liquid customers have off-loaded enough product to know what is required at thir location.

 

I deliver to a station where we back in, and its not level. Knowing that most fuel trucks are center unload, they built a concrete sloped ramp that we back onto. They were so kind that they even built about a 6" ledge at the back end of the concrete ramp, so we don't back too far.
It would have been cheap, and easy to do.
The trailer now level empties properly.
All businesses should do similar if its unlevel where trucks unload.

If it's a hose length issue, they can buy another piece to join on. If they can't afford 25' of hose, they are already doomed anyway.

 

Most I see are central unload on the side, so should not be a problem. I've never pulled a rear discharge.