The idea was inspired by the fact that the B-25 has a cavernous bomb-bay similar to the RAF designs, the RAF Mediums were built for strategic and tactical-bombing use (namely the HP Hampden and the Vickers Wellington -- though I'm not sure if they were classed as heavies initially), and the USAAF tended to favor some high altitude capability in strategic bombing designs.
While I know Martin did propose the XB-27 which was high altitude design, it appeared to have come after the B-26 design, and I figure a bump-up in critical altitude could be useful. There were numerous proposals made which included variants with single-stage/twin-stage and turbocharged variants of the R-2600 and R-2800. While I'm not sure how many turbocharged R-2800 variants were ready, I do know there was an R-2800 with a twin-stage supercharger available by May, 1940 (the F4U used it), and the B-26 made its first flight in November of 1940. It would have increased the plane's top speed and would have made it harder to catch, and with neutral blower, you'd probably retain good power even at lower altitudes.
While I don't remember the chart exactly, I do remember estimates of ram compression adding something like 2,000-3,000 feet of altitude. If this number is correct, you would see a maximum altitude around 800 feet higher (or 200 feet lower) than the F4U-1.
DarrenW,
pinsog,
S
Shortround6
,
wuzak