BF109K4 found strange add-on weapon variation, what the hell is that?

[FTC_Zero]

Was reading an mg151 article and found this picture. It said it is from a K4 but I never ever saw mg151 under a bf109. Do you have any further sources about that?

Edited June 4, 2020 by ZeroCrack01

[Kurfurst]

Its a modification tested for the G-4 at the start of 1943 with a centrally mounted 20mm gondola (originally intended for the Me 163) in addition to the wing mounted gondola. 

 

There was some talk about at Luftflotte 3 in early 1943 to equip G-3s with it with the MGs removed to lighten the plane, and G-4s for normal night and day fighter duties, but in the end the idea was dropped and this modification never seems to have been standardised or used.