Z-Axis Drive - - Tips and Suggestions

Here is a question I posted at the "CNCZONE" Forum, yesterday, with
no takers. Maybe I'll have better luck here.

I'm about ready to start construction of a Z-Axis Assembly from plans
purchased from Jeff Davis at www.homecnc.info .
I'll be installing it in a mill/dill (round column type) from Grizzly.

Has anyone built this, and have any tips, suggestions or
modifications, that I should first consider?

Looking over the plans, Jeff, seems to have thought of everything and
has come up with a very nice design.

My only concern at this point is to possibly come up with some way to
be able to maintain (or easily change over to) the manual operation
of the Drill.
Coming up with some way of disengaging the Z-Axis Drive from the
Spindle Clamp should be easy enough, its that blasted Return Spring
that has me stumped, rather it might fight the Z-Axis Drive or should
have some sort of disengagement, also?

Tom M.