I put a Big Dot on a 590 Thunder Ranch. Very happy with it, especially with that stupid standoff muzzle device that shrouds the outline of the stock sight.
Warning, installation and epoxy rant follows.
JB Weld works great. Note, fast cure epoxies are not as strong. Important: The biggest causes of epoxy failure are not mixing it enough and contamination. Don't rush.
You will replace the stock bead with a supplied smaller one. The original will unscrew but be careful! It is tiny and not strong at all. The new bead only locates the new sight so it does not need Loctite. Clean the base of the new sight and the barrel several times, only one wipe will just smear oil around, especially on a matte finish. Locate the sight on the barrel and put tape around the perimeter as if you were painting. Apply JB or other epoxy, do not starve the glue joint. You have already figured out how you want to hold the new sight in place, no need to smash it down hard, just firm so it is immobilized. Carefully clean the epoxy from around the sight, you can remove the tape now.
The pro touch. Most guys end up with a thin line around the sight from epoxy squeeze out. We can do better. Take a toothpick and carefully remove the squeeze out. Put the gun away and don't touch it for a full day, seriously.
Like a boss!