Empty wedge (and trouble creating custom lines)

I am trying to create variations of an empty wedge, but it has proven to be very difficult.

What I tried is drawing the shapes in affinity publisher and exporting them as svg -files. But for some reason my middle part is aligned higher than the others, and I can’t do anything about it. Could someone recommend a good workflow or solution for this?

moving the line in the line segment -editor does not do anything, so I should probably try to fix it when exporting the svg:

I wonder whether you could try using two of Dorico’s real wedge lines, one in black and another one in white attached at a slightly later rhythmic position (so it draws after the black one), scaled to (say) 98%, and positioned carefully in Engrave mode?