That is the problem with using "Square" for the diagonal cone, it leaves 3 squares of empty space within the dragable share (as square is larger than the original cone). So square is not the best solution.
Yes, that is what happened when I tried to add space for making the rotational point of the token match the point of origin (which makes placement easier, as drop-point = point of origin). Works flawless for the rotation, but then the empty space below becomes dragable. So not a good compromise:
https://i.imgur.com/eMBsvoA.png
This also caused the 45° rotated diagonal cone not to match. When you rotate the image via image software it leaves the upper part empty to match the original square image shape (which upon close inspection isn't even fully empty):
https://i.imgur.com/IBi09in.png
This in turn caused the oddities I was experiencing:
https://i.imgur.com/8zmWYJW.png
So I have to cut the upper free space out of the rotated image. The FGU cone shape is a bit smaller than the grid shape at the sides, while covering part of empty squares at the front. Nothing dramatic, though. But now I have to rotate all diagonal cone graphics by -45° and cut the (not so) empty space out. ;)
https://i.imgur.com/XipbhvX.png
Thanks for the ongoing support!