I believe the following is always true:
if $A$ is a Convex Hull of some points in $R^n$, then we have
$meanwidth(A)$$\ge$$C$$\cdot$$diam$$(A)$ ; (where the $diam$ stands for the maximum distance between 2 points in the same Convex Hull)
I need the above constant $C$ precisely, but I couldn't find any paper, text, book etc. containing the precise value of $C$. Any ideas?
Hug, Daniel; Weil, Wolfgang, $\textit{A Course on Convex Geometry}$. Very nice book if you are interested in Convex Geometry; explains the above mentioned property.