I think I made my tool because I was in a time crunch (as usual) trying to get my bike on the road, and tested before heading out on two super-century rides and two wicked hill climb days, all in about a week.

It was probably a Saturday evening when I discovered the problem of too big of spoke nipples for my stock red/green/black or even multi spoke wrenches.

The first incarnation was a bit loose
After the ride, I took a little more time to re-grind the tool and now it is very snug. I think with deep, slightly tapered sides which grab very well.

Initially it was made without the wings, and that should have worked, but Shimano also puts loctite on their spokes, and they were sized to make dishing difficult. Probably not anticipating dishing, but I had a special Franenproject that required it. The bolts sticking out make it work well. And nipple washers helped the dishing problem (with a lot of extra work).

Now, there is no real need to buy a commercial tool, unless I choose to look for a low-profile tool to aid with windup prevention.