No, I have seen perfectly suitable stern quarter outlets, bow and even side discharges with a center-line siphon break and a shut off seacock... I do prefer the stern though as do many builders who try and do it right..
Side discharges are my least favorite and I would personally avoid them at all costs on a sailboat. The proper installation of the siphon break gets difficult and can leave exposed hose visible in the cabin, to do a "safe" install for a side discharge..
I totally agree - but in an older boat there is not always a choice. If you hadn't guessed already, my suggested use of the check valve for a side discharge is to act as a 'flapper' to keep water coming back into the boat when heeled and the bilge pump is not running.. you still need the loop and siphon break.
Since the valve spends most of it's life above the water-line, there is no columns of water either side to hold it closed and the biggest risk is it perishing and failing open. Believe me, it's far better than having the boat threaten to sink under you.
Discharge into the cockpit is looking better all the time!
Bilge pumps to me are not an "after thought" they can be a safety item and one that should be taken seriously. Having had a thru-hull fitting snap, another story for another day, I do take bilge pumps and proper installation techniques seriously.
My main objection is using a check valve to keep your vessel afloat. But I am not alone on this and the ABYC concurs.. My only beef is the use of check valves on a primary bilge pump when that pump is also a centrifugal/Rule type.
I wouldn't like to suggest anyone relying on a check valve to keep your vessel afloat. For that reason, installation down in the bilge (as a 'foot valve') is a really bad idea!
I have less issues with them on rotary vane or diaphragm pumps because they CAN open them where the centrifugal often won't...
In my experience rotary vane or diaphragm pumps are more likely to blow the hose-end off the check valve if it fails to open... but if you are going to use them just make sure your piping can handle the output pressure, 'tis all.