I've built a "Varigrind" replacement, too. I've found that the angle formed by your tool's handle and the "leg" of the jig is what controls how far back the wings get swept. Moving the "leg" closer to parallel will "shorten" the wings, moving it more perpendicular will pull the wings back further. Changing this angle will throw of your tip's angle, too, so you'll need to readjust your distance from the wheel to compensate.
If you'd like to see what I built, here is a link:
That has all of the pieces of the jig I built, including the Fingernail arm. I'm in the process of replacing all the aluminum, but the principles all work the same