I'm running the Franklin Armory BFS-3, but I did strongly consider the Double Tap trigger.
You are correct that you do have to slightly modify the receiver to run the Franklin Armory BFS-3. It requires filing down one of the selector stops so that the selector switch will go past it.
The downside for me about the Double Tap was the trigger selector only offers the Safe position and the Binary position. You dont have the option of just your regular semi-auto fire.
The Franklin Armory BFS-3 selector allows Safe, Semi, and Binary firing.
Since I target shoot as well as squirrel hunt with my rifle I needed to be able to have semi fire without having to swap the fire-control-group out each time I wanted to use the rifle for a different purpose.
I think you will enjoy that Double Tap trigger though. It is a lot of fun to shoot 2 quick rounds or more when plinking cans or targets.