I have a Burris FastFire III on my SpecterDR and it works well. Initially I wanted to get an actual Docter sight but when I was shopping none were available so I got this thing instead. Yes you need to remove the set screws and use the new screws that are shipped with the mounting plate. Unfortunately I got mine probably 5 years ago and don't remember where I got it from but iirc it was around $80-90.
What mounting plate are you using? I have a Fastfire III and the mounting screws are too big for the mounting plate. I was thinking about going to the pic rail instead but I'm thinking it might be a little high.
Offset T1/RMR the piggyback option isn't optimal in my opinion having ran both offset and piggybacked options the offset you still have a solid cheek weld easier to transition to quickly and you don't have a huge height over bore.




























