gher.  Option '<a href="qh-optq.htm#Q6">Q6</a>' turns off merging of concave
facets.  This is similar to 'Qx'.  It may lead to serious precision errors,
for example,
<pre>
        rbox 10000 W1e-13  | qhull Q6  Tv
</pre>

<p>
<li><b>Maximum facet width</b> --
Qhull reports the maximum outer plane and inner planes (if
more than roundoff error apart). There is no upper bound
for either figure. This is an area for further research. Qhull
does a good job of post-merging in all dimensions. Qhull does a
good job 