We have 10 years experience of riding pretty closely together in staggered formation, the European roads are much smaller and more congested, a few times we rode side by side on the deserted roads.
The only time we got to close on this trip was when we suddenly hit the sudden Hail shower by Panguitch, we were doing approx 50mph, Isi slowed down and I was so mesmerised by the sudden change in conditions I had to brake a little to avoid her, the back locked up and slid out a little so I just released the brakes and took another line (very carefully) and we continued rolling about 10mph until we were clear of the shower.
Instinct clicked in, thats not something you can practise on these experienced rider courses, you either get away with it or not on each event