Tony, you might be interested in reading original sources rather than popular histories. From the USN post war analysis, what closed the mid ocean gap was short range carrier based aircraft, not long range aircraft. Take a look at
http://www.ibiblio.org/hyperwar/USN/...-51/ASW-6.html . Some interesting statistics here, from 1944 when the mid ocean gap was shut down.
Carrier based aircraft in mid 1944 made one sub sighting every 600 flying hours. 60 out of 68 sightings resulted in attacks (88.2 %). 40% of attacks resulted in a sinking. In other words, one sinking for every 600/.882/.4 = 1700 flight hours.
This is short range aircraft, with 1944 radar and searchlights, launched in response to nearby sub sightings. How can we reasonably expect a 1941 long range land based patrol aircraft, with lengthy transit times, to sink subs at 10 times this rate (according to your numbers)?
This same document has some interesting words for the British intiated practice of standing patrols over the Bay of Biscay in 1943:
"Allied antisubmarine forces inflicted the greatest damage on the enemy in the Bay of Biscay and its approaches as 14 U-boats were sunk in the Biscay-Channel Area and another six in the Gibraltar-Morocco Area. Although aircraft crews had to face the increased antiaircraft fire of surfaced U-boats proceeding in formation during the daytime, this presented them with a large proportion of Class A targets and over 25 per cent of the attacks resulted in the sinking of the U-boat. The crowning success of the month occurred on July 30 when a whole group of three outward bound U-boats was sunk, two by Coastal Command aircraft and the third by the Second Escort Group."
"
Four additional U-boats were sunk in the Bay of Biscay by Coastal Command aircraft during the first two days of August, and the U-boats were forced to change their tactics in making the transit of the Bay. They reverted to surfacing at night for the minimum time necessary for the charging of batteries and, in addition, hugged the coast of Spain to get as far as possible from Allied air bases."
The same source discusses the North atlantic sub battle in earlier years. Start at
http://www.ibiblio.org/hyperwar/USN/...-51/ASW-1.html , and read through to ...-7.html. The mid ocean gap was only one relatively small part of the total war in the North Atlantic. Closing the mid ocean gap earlier in the war could only have been done by moving resources from other tasks. Like your lengthy discussions of the land war in Germany late in the war, you keep suggesting one fix for one problem that could have lost the war for the Allies because of moving of resources from other problems. It ain't that easy.