I am confused.
A Spitfire with 85 gallons needs to be kept on the ground until the last possible minute because it doesn't have enough fuel to alter an incept point OVER ENGLAND by more than a few miles without running out of fuel, yet if we add
just 30 gallons or so it not only fly across the channel, it will be able to return from the Ruhr or beyond?????????
Common guys, you can't have it both ways, even with drop tanks/slipper tanks. A Spitfire could
cruise for over 2 hours after taking off, climbing to a nominal altitude (even if low) and still have 20 minutes of fuel left. Spitfire I's had nowhere near the appetite for fuel that later versions did at full throttle but shouldn't be that far off at cruise.
The problem comes in with that the cruising speed that gave it 2 hours of endurance was (even if fast enough to fly next to the painfully slow British bombers) was not fast enough to keep it from being a sitting duck if bounced by German fighters. It also does not account for combat. SO combat radius, like all other airplanes, is a lot shorter that cruise radius (range/2)
Over England there is another squadron coming (hopefully}) to relieve or beef up a defending British squadron, when flying escort there is no ready relief (one reason Fulmars and Wildcats) got such large quantities of ammo, to keep the fight going if need be). Yes you can use relays but the units doing the 2nd or third turns at escort had to take-off well before the 1st escorts are in combat, If they push too hard to join the fight they cut into their endurance on their turn at escort (or their ability to get back)
There were no 2 blade wooden props left in 1940, however you can't go back and change the initial requirement. You also have 1939/early 1940 when many
service Spits and Hurricanes had 3 bald 2 pitch props, fortunately very few had to go into combat that way in England.
But the better props helped handle the increase in weight due to the armor, BP glass and self sealing material.