How low do you want to go?
There are a few ways to make the Glanza go low, but the problem is that you have to give up damper stroke travel to accomplish that.
When we design the MeisterR Zeta-R coilovers for the Glanza, we made the rear as short as possible while retaining as much damper stroke travel as we can pack in the given space.
You can take out more travel to lower more, but in return you have to loose some performance which isn't really worth it.
But if you have a "specific" goal in mind, I am hapy to help if needed.
Best Regards,
Jerrick