I wouldn't consider the XP-42 as a failure as it succeeded admirably in it's intended role, a test airframe.
It was never a full-blown project for a new pursuit type. The XP-42 was actually the fourth production
P-36A and lasted in the test world until the summer of 1947. It tested a wide variety of cowling, cooling,
propeller and exhaust systems as well as an all-flying horizontal tail.