Much less skin area on that fuselage, narrow and not very tall. Cockpit is low, sp very low drag.
Likely to be have been fast on 1100hp of the early Allison.
We can use the XP-39 as reality check. As rolled out from Bell factory, it was good for 340 mph, unarmed. So it got shipped to NACA for a clean-up job, who made a full list of recomendations in order to bring it to the promissed 390 mph at 20000 ft. XP-39 have had a far smaller wing, and much thinner (15% at root vs. 18%).
So let's say Bell rolls out the Model 3, and it does 325 mph. Shipped to NACA, tested and modifed, they manage 375 mph after all is said and done. Then we add armament - 360 mph?
Big wing, good for high altitude where it was to be operating at. Later Bell P-39 testbeds for the Continental Hyper Engine had increased wing thickness from 15% to 18 for more volume for fuel tanks, and to increase strength of the wing, carried over to the P-63 that had very effective ailerons, to one of the fastest rolling US aircraft of the war
I have no problem with wing being big and thick
if engine makes abundant power at desired altitude. 1100 HP will not cut it just because 2000 will.
Unike the XP-39E, the P-63 have had laminar-flow wing, and still was barely good for 400 mph in A version.
Yes but at the time twin engine fighters were being designed you couldn’t actually replace them with single engine aircraft, Thatcis why we got twins. No one LIKED twins at the time. As stated the are more expensive, use more resources and take more maintenance and are not as maneuverable and present a bigger target.
But a less maneuverable twin is a better option to fight your enemies with then an airplane that had to turn back 200 miles ago.
And twins will ALLWAS have more range (all technology being equal) as they have more power and can carry more fuel as a result, It is only when the power/fuel efficiency of a single gets to the point that it can do the job needed at the range required that they go out of favor. The obvious example being the long range escort of the Mustang. But even that had its limit as witnessed by the Twin Mustangs.
How much of range is needed? We have not just the Zero, but also Ki-43 and Ki-61 having combat radius (= fly out, escort bombers, fight, RTB)
of beyond 600 statute miles at low altitudes, on engine and aerodynamics from late 1930s. That is more than enough for UK, Germany, Italy, Japan and Soviet Union. And USA, once they figure out that bombers actually need escort.
Not just Japanese did it, French produced D.520 with 50% more fuel than what will Hurri/Spit/109E carry, ditto for the Italians with Re.2001, and for the US with P-36/40. Even the P-39C was carrying 170 gals internally.
Mustang was carrying 180 US gals of fuel with V-1710-39, a 2nd or 3rd rate engine by standards of 1942.
So the only way you are going to eliminate twins is by either having a short ranged war (or at least expecting a short ranged war) or by somehow inventing a more powerful fuel efficient engine a lot sooner. And even that probably won’t work. As the US (at least) has very long distance between it an potentially enemies. With those big ponds. And the US was getting into long range bombing so until the fighters could escort the bombers all the way the US was going to keep pushing for greater range (as in the twin mustang).
So until the range of bombers and fighter match you will see interest in longer ranged fighters and bigger fighters can carry more fuel but need more power and thus two engines can help...
As noted above, USA was the only power contemplating international bombing campaig, and even the post-war Twin Mustang will be unable to escort B-36s from CONUS to Europe. Pre-war, nobody in the USAAF was thinking of bombers needing escorts, and accordingly was not requiring any of the like from industry to design & produce.