Air combat over Bulgaria on 11th June 1944

[Burdokva]

I've recently started a research that, to be honest, grew from a simple project to find a "Balkan Pony" scheme for a 1/72 P-51B model, to a long study on the aerial warfare over the Balkans, and Bulgaria in particular during 1943-44.
While in recent years many new, and excellent, volumes (predominately Bulgarian) dealing with the subject have appeared, there is always the issue of claims of aerial victories and actual planes lost on both sides. Cross-referencing the data from both the USAAF and VnVV is quite hard due to a variety of reasons, but I've already found a lot of info (currently I'm tracking down downed US Fighters.)

I'm particularly interested in the air combat on 11th June 1944 over central and western Bulgaria. A single plane was downed (by poruchik Ivan N Bonev with Bf 109 G6) over Sredna Gora Mountain (according to Bulgarian sources the fighter fell down engulfed in flames). This is almost certainly the P-51B-5 (ser.43-7024) of Joseph F Riley from 2FS, 52nd FG listed as "KIA" over Sofia, Bulgaria on 11th June 1944. Both the 2FS and 5FS were involved in the fighting over Sofia that day. Could anyone share any combat reports or memories of the fighter pilots of the 52nd FG?

Any chance they again fought the Bulgarians on 11 August 1944? I am looking for any clue on who shot down poruchik Bonev on that day, two months.

EDIT: Again, I forgot to mention - I'd be happy if anyone has a colour profile or a photo of Riley's Mustang!