Wonders on Z axis

[LabSkis]

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.


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:



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.


Can I increase it?

Other solutions you have used?

Thanks