Dora-9,
I can't help with your question, but it's a lovely photo of a "loose battle formation".
If any of my instructors had been flying, the wingtips would have been overlapping!
I was once in a cross-country flight of four Chipmunks being ferried to Binbrook for a UAS Summer Camp. To impress the locals (tough to do when you are arriving at a Lightning base!), the Boss had briefed a run-in and break.
On arrival at Binbrook, the instructors formed up into a box and we descended in very tight formation at about 120 kts. My instructor, who was no slouch at formation flying, was a bit concerned about No. 4, whose propellor was underneath the Boss's tailwheel!
I wish I'd had a camera.