In my last post, I left out the XF-41's specifications, as well as a few more facts that I would like to include. Its top speed was 470mph, service ceiling was up to 50,000 ft. (even though it could have actually gone higher, they did not take it up further for safety reasons, although a modified XF-41 was used for extreme high-altitude tests in the 1950s, where the information was passed on to NASA but without revealing the aircraft used) and armament was two 20mm cannons.
One prototype was fitted with jet engines, but the "zone of perfection" was upset. An unmanned test airframe took off under remote and flipped on its back the minute its gear lifted off the ground, confirming that the XF-41 could not be fitted with jet propulsion. Some small changes could be made, however, one XF-41 was successfully flown with five .50 caliber machine guns instead of the original two 20mm cannons, but any changes to the basic design of the airframe were invariably disastrous. The "zone of perfection" itself was the XF-41's greatest advantage and the entire essence of its design, but at the same time its greatest enemy-completely putting away any development or modification potential-Andrew