Update dactyl.clj

Added a 6th screw post near the middle of the back wall

src/dactyl_keyboard/dactyl.clj

@@ -1350,9 +1350,11 @@
 ; Offsets for the screw inserts dependent on thumb-style & inner-column
 (when (and (= thumb-style "cf") inner-column)
     (def screw-offset-bl [9 4 0])
+    (def screw-offset-tm [9.5 -4.5 0])
     (def screw-offset-bm [13 -7 0]))
 (when (and (= thumb-style "cf") (false? inner-column))
     (def screw-offset-bl [-7.7 2 0])
+    (def screw-offset-tm [9.5 -4.5 0])
     (def screw-offset-bm [13 -7 0]))
 (when (and (= thumb-style "mini") inner-column)
     (def screw-offset-bl [14 8 0])
@@ -1372,6 +1374,7 @@
          (screw-insert 0 lastrow   bottom-radius top-radius height screw-offset-bl)
          (screw-insert lastcol lastrow  bottom-radius top-radius height screw-offset-br)
          (screw-insert lastcol 0         bottom-radius top-radius height screw-offset-tr)
+         (screw-insert (+ 2 innercol-offset) 0         bottom-radius top-radius height screw-offset-tm)
          (screw-insert (+ 1 innercol-offset) lastrow         bottom-radius top-radius height screw-offset-bm)))
 
 ; Hole Depth Y: 4.4