How to make windows join block based on Blockbench model?

Hi. I've created some 3/4 depth blocks (.75m, 12pixels) from models in Blockbench. But the window/glass pane function does not recognise them as regular blocks so won't join the windows...

I can't see any option in MCreator relating to window functions (I tried "Check this to enable connected sides" AND set the bounding box to be 1x1x1). Is there a way to do this or will I need to create some custom models/blocks for the window panes?