plotting - 3D arrow tail properties

I would like to use VectorPlot3D to plot a vector field with 3D arrows:

B1 = 0.0005;  (*G/μm*)
B2 = -2*B1;
b[x_, y_, z_, Bf_] := {B1*x, B1*y, B2*z + Bf};

VectorPlot3D[b[x, y, z, 0], {x, -13, 13}, {y, -13, 13}, {z, -13, 13}, 

             PlotRange -> {{-13, 13}, {-13, 13}, {-13, 13}}, 
             VectorScale -> {0.1, 1, None}, VectorPoints -> {6, 6, 5}, 
             VectorStyle -> {"Arrow3D", Red}, 
             RegionFunction -> Function[{x, y, z}, x^2 + y^2 + 2 z^2 < 13^2], 
             Boxed -> True, Axes -> False]

Is there a way to change the properties of the 3D arrow tails? For example, to make them thicker.

I'm guessing it has something to do with the Tube[] function, but I cannot quite figure it out.

Thanks in advance!

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