@HS_Kim, you have inconsistent widths in the panels, because the untrimmed surface is larger than the actual filletted rectangle.
Same with @anon39580149’s solution if D is larger than 2…
From here: Shrink trimmed Surface in Grasshopper
(A reparametrize is needed after the shrinking…)
private void RunScript(Brep S, ref object T)
{
S.Faces.ShrinkFaces();
T = S;
}