I am happy to report that the Millet 30mm steel rings arrived, and they are working wonderfully.
They fit the Tasco PDP3 nicely, and are made very well. They have several nice design features, and are machined and finished in a high quality manner.
Interestingly, they have a "clamp" and allen head screw on each side of the base mount, which can be a blessing and a problem. The blessing is that by adjusting both sides, you can surely "center" the rings on any weaver style base, but the problem is how to be sure that the two rings are "centered" equally. You wouldn't want to be putting stress on your sight by having the rings "out of line".
The instructions tell you to only loosen the right hand screws, which would reduce the chance of getting them out of line, but I could not mount them without also loosening the left screws. But I counted the "turns" as I loosened them, and turned them back the same amount when it was mounted. This has seemed to keep the rings in line when I tightened the right side screws.
The ring portions have a raised square section around the screw hole on the bottom half, and a matching relieved square in the top half. As the rings come together, these keep the two halves "locked" in alignment even if they don't close completely. They came with two black self adhesive strips in each ring that I assume is for "shimming", but they are not mentioned in the installation instructions. I imagine they could also be "anti-slip" strips, but I'll wait and see if I need them.
And they worked well at the range. They are mounted on my 6" S&W 686, and I sighted it in at 25 yds. Although I am still having trouble keep my all my shots in the bullseye, I am getting better groups already, and I hoping the bullseye problem can be helped by practice!
Maybe these steel rings are a little heavy, but they sure work well. Thanks everyone for their advice and suggestions, I know a lot more about this topic than I did before.
And I guess I still have one question, if anyone reads this far, once I've sighted the gun in with the red dort sight, how should I "secure" the rings? Should I loosen the various screws, one at a time, and re-tighten afgter applying some blue Loctite? Or should I try to secure everything the way it is now, like by putting epoxy or paint on the screw heads? And a third choice, I believe there is a "new" Loctite for assembled pieces, that I imagine seeps into the threads. Any suggestions?