NitroX
I have spoken with the maker that I mentioned in my previous post and he assures me that all of the dr's that he has produced and to the best of his knowledge, all dr's are regulated and designed to shoot right barrel first ie front trigger first then left barrel rear trigger.

The only exception is that if a left handed shooter requests it, he will regulate the rifle for left then right barrel but will also flip the triggers so that front trigger activates the left barrel and the rear trigger activates the right.
I know that this is only one maker but I do trust both his knowledge and experience.

I dont pretend to be an authority on the subject but I am certain that he is and my comments in my original post were based on information I have picked up from him over the years.

hope this helps

DT