[trebb]

Probably about 100’ apart - they are a bit bigger than they look and seem to be almost touching during air shows even though they are usually 60’-70’ apart.

[Hulka]

If they are flying fingertip in an airshow, or during weather penetration or escorting another squadron-mate, then there is a 3’ separation between the wing-tips.

In the picture here, not sure, but pretty close, less than 50' and my guess is loose fingertip meaning about 20-30' between wingtips.