I found a solution and sharing it here if anyone is looking for it.
If you must use solids for LoS, then create 4 imagepoints for the solids and set them at the four corners - top left, top right, bottom left, bottom right.
When checking for LoS against this solid, use the Has LoS on position and check all 4 positions using an OR. If any of them is True, you have LoS.