+mainframeholex = backslotedgespace/2 + slotpluglongerlen * slotxperlen
+ + 0.5 * slotwidth * slotyperlen;
+
+mainframeholey = -slotpluglongerlen * slotyperlen
+ + 0.5 * slotwidth * slotxperlen;
+
+mainframemaxx = mainframeholex + mainframeextraside;
+mainframeminy = mainframeholey - mainframeextrafront;
+mainframemaxz = keepslotstartz + keepslotlen;