I recently purchased BR-R7000 the 105 version dual pivot brakes. There are 6 caliper retaining nuts included in 5 different lengths.
They are all the same diameters, just different shaft lengths.
Nut Head = 10.00mm diameter (3.05mm long)
Nut Shaft = 7.85mm diameter (various lengths)
It sounds like the head is expected to remain outside the frame hole on your setup.
Barry
Last edited by Barry2; 06-24-20 at 05:43 PM.