Help orienting box to grid; populating city blocks with building forms

I’ve been working on a building generator definition to populate city blocks with various sized units. The idea is to be able to select the perimeter curve of a block and have the building types automatically populate the area based on a simple orthagonal grid. It won’t be perfect but it will at least be a reasonable approximation of existing conditions and allow us to perform our analysis by giving us actual building geometries.

I know I’m close but there are a few issues I’m having. I’ve decided for time’s sake to only focus on populating each block with one type of building. In the definition attached I can set the dimensions of that building type, successfully populate the block (surface), and trim the buildings to fit only within the block. However I can’t seem to figure out how to orient the buildings to the grid and still maintain the full count within the block.

So right now I can populate the block but the buildings are in this checkered configuration shown in the first image; this results form setting the baseplane of the BOX component as the points of the PTTRIM component. To remedy this I thought setting the plane of the BOX component as the polylines generated from the PTTRIM component would work, however you’ll see in the second image that I get the proper orientation but the remaining buildings disappear.

So then I tried setting the baseplane of the BOX component as the panels generated from a SUBSRF (ISOTRIM) component because I knew they would be fully populated. The problem there is I get an error from SUBSRF component saying “1. Subsurface is invalid because the trimming V-domain is singular.”As usual I feel it’s a simple correction but I’ve been banging my head against many attempts/versions of this definition since noon yesterday and I can’t seem to work out the issue.

Thanks to anyone who can steer me in the right direction!