[F19Gladiator]

Until reliable documentation appears – I have problems with the theory of adding a weight and drag increasing belly gun pod on a reconnaissance Bf109 in order to fight off potential aggressors coming in from dead behind.
A recon aircraft relies on well adapted tactics for a specific mission to limit risk of detection and exposure to counter actions from the air as well as from the ground. High speed, altitude and acceleration being some of the survival factors why recce aircraft rather tend to delete guns and ammo to save weight, take away not needed drag inducing gear on the airframe, covering not needed gun ports as well as keeping the surface smooth and even waxed and polished to gain some extra km/h airspeed. If we accept this as being correct, which I believe a recce pilot can confirm, adding a gun pod under the fuselage would be extremely counter productive.
The value of this armament was found disappointing when tested with the Bf 110 in 1941/42 as described in my post at LEMB and I would be surprised if it would have been found of better value with the Bf 109, which design logically to a lesser degree would benefit from such a weapons arrangement as being more agile and thus potentially more easily avoiding being shot down from behind compared to the Bf110 which in turn already had a rear gunner for defense at this weak spot.
From the aggressor's point, intercepting a high flying recce aircraft most often meant climbing up to the altitude of the recce aircraft from beneath if not an altitude advantage for the interceptor existed before the chase started. This has the advantage for the interceptor of not being easily observed by the intended victim while approaching, and in case it was spotted it inevitably would make the recce aircraft accelerate its speed and vanish.
The final attack can for example be from a gained height advantage by building up speed in a dive towards the fast recce aircraft and open fire from slightly above, alternatively diving under the recce aircraft gaining a speed advantage, nose up and attack the belly of the recce aircraft. In case it comes to a level chase the interceptor can stay slightly below the recce aircraft thus being more difficult to observe and if the recce a/c maneuvers to spot the interceptor it will lose speed which is to the interceptor's advantage. Staying right in the prop wash from the aircraft in front is not ideal from an aiming point either, why again opening fire from slightly below or above would be to prefer. Given this I believe the rear-firing gun concept on a Bf 109 was a still-born idea.
Would be interested in hearing your views on this.
Best regards,
Goran