"not very good" is a bit nicer than I would have been
It also works with/makes not-useless the Powerful/Equine Build racial abilities.I have to confess I wouldn't have thought of putting in rules for going piggy back though. Using mounted ones makes sense and put lots of comedy with the reduce spell back on the table.
NB, I suggest you give the Equine Build ability to ponies, mules and donkeys.
A corpse is an object rather than a creature, so the rule does not apply.Until the party has to get the dead party member back to town.