Going to jump on the soapbox for a second.
It is a wonderful Country where people can own what they want and not what others tell them they should have.
Just as Congress should not tell us why less cartridges should go in our "magazine clips." Our fellow enthusiasts of the Shooting Sports should not tell each other why they should not get the handgun they want.
I love snub nosed magnums. I do not care that I can get more velocity from a 6" or 8 3/8" barrel. You 6" and 8 3/8" guys can get more velocity from a 16" lever gun. That does not make your hunting revolver useless.
Let us hope that it stays that way in America. OK, I am stepping of the soapbox
The problem is that you are porting an existing barrel. That limits your choices. In addition to the dual or quad slits in the barrel (like Mag-Na-Port), there is hybrid porting.
Schuemann Barrels in Washington made hybrid porting famous. Though these days he mostly does auto barrels for sale to gunsmiths. There are some folks copying the concept. Hybrid porting is probably cool enough for you.
If, and that is a BIG IF, you can find one of the 3" barrels with the power port you could just have them swapped. Then you would have a single expansion chamber compensator out in front of the sight.
I have one of the 4" GIGN power port barrels just waiting for a 586 to put it on.
Here are various factory and aftermarket ported revolvers for you to think about.