Guys,
In making double set triggers, I have found it best to simply make a copy of an existing design. Buy a well made set from TOTW or whoever, and than use it as a pattern to reproduce your own. There is no need to "reinvent the wheel", if you know what I mean. Here is a photo of a German rifle that has a double set trigger that I copied, or adapted, from the modern made one with that laid back rear trigger. If my memory is correct the modern one uses music wire for the front trigger spring and I actually used a flat spring for this. Actually, I found it more challenging to put that dratted - blasted - frustrating little detent into the lock tumbler than it was to make the set triggers. The hand forged lock shown is done in a similar way, just a copy, or adaptation, of the large Siler.
Jim