Tap Plastics did a good job. Nice, smoothed-out edges, nothing sharp. I love that I can take any kind of odd idea to Tap Plastics and they can make just the thing I need.
So I tried out the template on a couple of my hexagons. It was then that I discovered I didn't have any of the tacky plastic stuff to put on the bottom of the template to keep it from slipping as I used it.
Double-sided tape to the rescue!!! I don't suppose I'm the first person to ever use this as a substitute, but it worked fairly well. I've trimmed about 50 hexagons now, and it is still sticky enough. It's also cheap and easy to replace the tape when I need to.
Another wish in my little mind was that I had one of those turntable-type cutting mats, since there is a lot of turning with all this trimming. I live near some great fabric stores, but they are not your average quilting store (nor a Joanns) and neither shop carried this type of cutting board.
So I improvised again by placing a small towel under the cutting board. Then I simply spin around the towel, cutting mat, and everything when I have cut all I can reach, and need to turn it to trim the other side.
Here is an untrimmed stack of tumbling blocks (photo on right). There are some points sticking out, and a lot of uneven edges.
After trimming, the stack looks like this photo, everything the same size, with edges nice and even.
I think I will need all the help I can get to make this quilt top without puckers and lumps in it!

And I am left with this nice jumble of confetti fabric scraps! I think
it's quite pretty, and even MisterStitches encouraged me to save the scraps till I get all done. But whatever will I do with them? I suppose I could use wash-away stabilizer and sew them all together to make ????