One advantage of cabosil and similar fillers is that you get an enormous amout of filler from the epoxy. You just keeep adding and adding and adding until it finally gets thick enough. You make a lot of volume. With a wood flour, you'll get about a fifth of the amount of putty from the same amount of epoxy. thus the cabosil filler is lighter - that's why it's invented. I usually add wood flour to a putty mixture when I made enough with the cabosil. It will immediatly tighten it up. Wood flour is also a by-product of fine sanding and cheaper and easier to make for the manufacturers. Raka just gives it away sometimes with orders. It's maple dust and it's really fine.