I would say that Lead & Follow has to be performed as close as possible between the leader and the followers. Absolutely not more than within eyesight and therefore is there no need of any technical devices more than a radio. In worst case is a GPS with some fixed turning points enough to communicate distance and bearing to close the separation.

What happens if the distance becomes to big (10-15km) and I as leader finds out a good climb? I will take it and most likely leave it until the followers are there, they will only get the information of where it was as good climb, not if it still there and how to center it. They will stay for a while and struggle, perhaps find it a go to could base and in worst case abandon it and follow me on the lows. At the next thermal I find will the separation be even bigger and the follow & lead will fail unless I pull the brake and take away 500m+ in height.

Lead & follow has to be performed in a closer configuration, max 2-3km in distance and ~100m in height. If the separation becomes bigger do the leader have a few options:
- To try a weak thermal which I might not have taken when alone, to give the followers the time to catch up
- Stay at could base to wait until the followers has the same height until leaving
- Pull the brake to get to the same height and together make a save from the lows
- The follow have to follow all the time. Any kind of sidetrack will make the sepperation bigger.

To a surprise for many can this be performed with quite big differences in glider performance as long as the wing load are in the same range.

This art of soaring is not easy, it has to be performed with discipline and with respect to all in the team. The leader has the respect that the followers are not equally skilled in finding and centering thermals and the followers has to dare to follow the leader into unknow areas (without compromising the safety). It is also essential to prior the flight agree on how to communicate on the radio, misunderstandings are not helping when the situation becomes stressed.