I will also love to paint with one ink like Toni. I have an AxiDraw V3/A3 and i tried to use de recommendations but unfortunately it did not work for me. In wcb_conf.py I changed the N_PAGE_WIDTH to 8In and the F_DPI_16X to 2874 steps. Then i changed the wcb.py from SM to XM. The scale seems to be correct but the drawing seems to be rotated 45°. With the Control watercolor i can move manually in the x and y axis without a problem.
I am using the Control WatercolorBot inkscape extension Release 1.6.0
Thanks in advance!