Right, so pins are mounted and now for the test of "does it fit as intended?"test.
It passed with Flying colours!!!

Its a little tight when the backplate is cold but as soon as it heats up it releases as soon as the camlocks are released. Guess it was because i was test fitting while the backplate was warm from machining.
Fitted the backplate to the spindle and started to machine it flat and the boss where the chuck must fit. Its an old Rhome 4 jaw scroll chuck that was heavily beaten in its previous life, got it with the Chipmaster , unmounted.
Got the chuck to fit nice and tight and then took out the jaws to face the craters and other dings a bit smoother.
Next step is to grind the chuck jaws as they have had a rather tough life. I need this chuck operational as i currently only have a 4 jaw independant and quick setup is still something i aspire to.