Although not a large aircraft, the HS125 cockpit layout means that it displays many of the difficulties mentioned when trying to conduct formation flying. We gained a wealth of experience in formation flying while operating the 200 Series for over 43 years. One thing that has not been mentioned is where the handling pilot should sit. It was found that it was always better for the handling pilot to be in the seat closest to the lead, ie echelon left sit in right hand seat. I was quite content to be right hand seat captain and handling pilot.
I know that some of our “God Given” QFIs said that they were happy to fly cross cockpit, however, few could perform as well as they thought. The general trend would be to drift wide and ruin the shape of the formation. Cross cockpit could also lead to high excitement if one were to get out of position and then the leader started an unexpected turn. Cross cockpit flying permits a far shorter time before one is “lost lead”.
Flat turns require a lot of practice and allow little margin for error when flown in the correct position. A loose flat turn may be employed, however, lead/lag and rate of closure have to be understood. One may suggest that echelon turns of more than 2 large aircraft needs a smooth leader and a lot of practice.
I was amused by the suggestion that Fast Jet TPs would be great at close formation. I have witnessed a few would are very mediocre, particularly when conducting AAR. There are many line pilots flying various models of Airbus who have far greater formation handling skills.