I had my accushadow milled for a dot and thus removed my stock front sight. I took an old SP01 sight and ground off the post to eliminate any cowitness opportunity. I was picking up the front fiber optic sight as the dot and it was messing with my eyes. I now have no backup iron's on my competition rig. I run the SRO so hopefully it holds up (has for almost two years now).
Come to think about it, the dummy sight base does just slide into and out of the dovetail easily. I have to keep an eye on it when cleaning so I don't loose it. I don't recall fitting it much, but maybe I did so it wouldn't be a pain to swap between the dot and iron's?
Maybe you will have to deform the dovetail on the new sight to give it an interference fit in the slide (assuming you have the correct dovetail sight already)?
Good Luck!
Toby