It's nice to hear that you use Voxelizer for some other printer than Zmorph - although we primarily support the Zmorph printers, Voxelizer is designed to work with any 3d printer that uses standard gcode instructions.
Actually, the feature you seek already exists in Voxelizer, but it is not very exposed.
In order to change the print table dimensions do the following:
1. Open the folder My Documents/Voxelizer/Printers (or the equivalent on Linux/OS X)
2. Copy-and-paste one of the .xml files, for example zmorph.xml
3. In the copied file, change values of name, x_size, y_size, z_size to fit your printer's dimensions. Other fields are not currently used, so there is no need to change them.
4. Open Voxelizer and click on the icon near the top of the window
5. Choose the newly added printer - the choice will persist between separate Voxelizer sessions.