MILLIPEDE Topology Optimisation Won't Work Inside Boundary

Hi all, I am trying to use Millipede’s topology optimisation capabilities to create geometry within a relatively slim boundary; shown below.

The issue is that the ‘Get Channels’ node comes up with an error saying “This component only works on single voxel fields”. Error shown below:

How can I fix this? I will really appreciate any help with this issue! Thank you.

GH Script attached:
A.Hillary Millipede Topology Optimisation for GH (115.1 KB)

P.S. Also, if anyone has any suggestions of other methods of topology optimisation inside of grasshopper I would be very interested to hear about it.