Pete

There is no question. A Double is set up to fire the front trigger first. You should be putting the trigger at the front joint of your finger. If you do this it won't slip off.

It is not a hair trigger so it just the tip is not needed. If you feel you need to cross hatch the trigger go ahead but then you need to disassemble the action, black the trigger and you end up with something the next guy may not appreciate. Better to concentrate on the correct method.

If you search the question here you will find many discussions of this but always the same conclusion.

Use the rifle the way it was intended and built.