Watson ... your OBWs are going to be spectacular using that main fabric.
Using your pic, I patched them together, and am attaching two mock ups for you.
Personally, the coloured tris distract me from the beauty of the OBW centres.
Though I do like the dramatic effects created, with the black and lavender (is it??).
So who knows, I may change my mind on it.
Agree, it would be nicer to finish each hexie before joining together.
I have seen that accomplished with 1/2 triangles on the corners of the hexies.
Maybe you can doodle and figure it out with this triangulated graph paper?
https://incompetech.com/graphpaper/vartriangle/
Look forward to seeing what you create!