11. The assembly of claim 8 , further comprising the upper compression structure including: a) the upwardly projecting structure is a pin that extends upwardly and is sized and shaped to engage the inner fastener lower through-bore; and b) a pair of downwardly extending leg portions joined by a lower U-shaped surface so as to be adapted to engage and partially encircle the connecting member.
11. The assembly of claim 8 , further comprising the upper compression structure including: a) the upwardly projecting structure is a pin that extends upwardly and is sized and shaped to engage the inner fastener lower through-bore; and b) a pair of downwardly extending leg portions joined by a lower U-shaped surface so as to be adapted to engage and partially encircle the connecting member. 13. The assembly of claim 11 , wherein the upper pressure insert includes a substantially planar top surface, and the upwardly projecting structure is a pin that has a base joined with a central portion of the top surface.