Wonders on Z axis

Hello,

I am designing an aluminium frame CNC.
I will post someday pictures of the full machine I intend to do.
For the moment, I have troubles with my Z axis design that you can see below.

Attachment 3875
For those who know, I have used carriages from Ahren Cncrouterparts.
My concern: how to get the maximum travel on z axis.
Lets have a closer to my design:

Attachment 3876

On this picture, I have put the z axis as low as possible.
For me, the available travel is min 30 mm (cf. picture), depending on the length of the bit I will use.
How can I increase this travel?
Fix my router further down on the interface plate? I fear cantilever...
For the moment the router is fixed 30 mm below the carriage.
Attachment 3877

Can I increase it?

Other solutions you have used?

Thanks

Mount the motor for max travel refererenced to the vertical mount extrusion. Cut the plate off flush with the motor mount and part off the drive shaft as short as possible?