Ok using some of Jazz's Suggestions, Ive reworked the Z axis and included all machined parts im hoping to end up with.

Click image for larger version.  Name: backplate wide mounts mk1b.jpg  Views: 437  Size: 250.1 KB  ID: 7810Click image for larger version.  Name: backplate wide mounts mk1.jpg  Views: 450  Size: 271.8 KB  ID: 7811 Click image for larger version.  Name: backplate wide mounts mk1d.jpg  Views: 446  Size: 286.1 KB  ID: 7808Click image for larger version.  Name: backplate wide mounts mk1c.jpg  Views: 453  Size: 291.9 KB  ID: 7809Click image for larger version.  Name: backplate wide mounts mk1f.jpg  Views: 434  Size: 223.3 KB  ID: 7812Click image for larger version.  Name: backplate wide mounts mk1g.jpg  Views: 440  Size: 173.8 KB  ID: 7813Click image for larger version.  Name: backplate wide mounts mk1h.jpg  Views: 410  Size: 156.6 KB  ID: 7814

Im Hoping Thats better than my first attempt, i've put pockets in to remove weight, whilst trying to maintain structural integrity..

Rick