I have a 686 Hunter and a 629 Competitor plus some others with the barrel rail, if that helps. And an Ultradot Matchdot II and an Ultradot6. Just not a 1" version. But they all come from Ultradot with rings included. Mine have been what would be classed as "Low", and generally fit, except the Ultradot6 now wears higher rings, but I can't remember why, as they're not needed on the 625-7 where it now lives.
So, IF you go with the 1" tube, why not give the factory rings a try, first?
But having thought about it a little, I'd recommend a 30mm tube lest you feel like you are trying to look through a drinking straw! That 1" tube reddot way out on the barrel is going to be pretty slow and the field of view immediately surrounding the target will cluttered by the optic housing itself. Seems best to save the small tube for use when it's nearer your face, such as on a rifle receiver.
FWIW, most of my barrel mounted reddots are Holosights. C-More sights are good for this sort of application as well. They do sit higher, though, but i still find them easier to utilize than the tube types. Situation is less cut and dried when the sight is on the top strap.