First European Pen Question

Hi all, received a Jet mini lathe for Xmas and have just started pen turning. Slimlines and Perfume Pens I have found to be relatively easy. I have started on my first European Pen (Timberbits kit), have turned it as directions indicate. My question is to do with the centre band. Have made a tenon 3mm long on the upper tube and the band fits snugly. Should this tenon be 6mm which is the width of the band or reduce it mating surface on the lower tube?. By the way the timber I am using is Padouk that I had left over from one of the many boxes I have made.

First European Pen Question