I found this
Aviation Forum thread on SAAF lightened Spitfires and thought one would make a cool skin.
The South African Air Force's 10 and 41 Squadrons were based at Idku in Egypt from late 1943 to 1944 and were tasked with defending the Suez Canal. The Luftwaffe were still sending Ju-86R spy planes over to check on Allied ship movements. These aircraft were the U-2s of WW2 with pressurised cabins and high compression diesel engines allowing them to operate at over 40,000 ft. To intercept these aircraft the Idku Wing set up a flight of specially lightened Spitfire Mk IXs. These had reduced armament, no armour and all the paint including RAF markings removed. A tactic was devised where three aircraft would take off together, but with only one equipped with a radio. Once visual contact with the enemy was achieved the lighter radio-less aircraft would climb to intercept. The lightest of these had only 2 mgs and would force the enemy make evasive mauneuvers and so lose altitude. It would then be finished off by the second cannon-equipped aircraft.
On the 15th April 1944 a Ju 86R was successfully intercepted at 45,000 ft but not shot down. I suspect this may have been down to gun freezing, a common Spitfire problem at high alt. Now they knew the Ju-86R was no longer immune from interception the Luftwaffe stopped their reconnaissance missions over Egypt.
This particular aircraft MA504 was cannon-armed and test flown up to 47,000 ft by the Idku Wing's base commander, New Zealander Wing Commander Dereck "Bill" Kain.
