The face of the 44 1/2 hammer listed on cpa is different than the 44 hammer. I wonder if it would effect the way it locks up?
Can you send pics of the two hammers you have?

OK, I've pulled out a hammer from an original 44 1/2 DST action to compare, as well as a "CPA repreoduction" 44 1/2 DST hammer.   

The reproduction hammer fails congruency with the 44, because CPA used a smaller diameter hammer pivot screw.

Although the original Stevens 44 1/2 hammer has a somewhat less upright hammer spur, and the location of the full-cock notch looks a little different, I've assembled this original 44 1/2 hammer to my 44 DST action, and it works, still using the sear from the 44 DST action.  What more can I tell you?.  Tell Gail you need the hammer and fly for an original 44 1/2 action, not one from their reproduction.   

---------------

As an aside: I bought a complete 44 1/2 pistol grip tang DST setup for CPA's reproduction 44 1/2 some years ago, thinking to fit it to an original 44 1/2 action.  Doesn't work.  CPA has changed the tang forging shape in subtle ways that make it all but impossible.  I've modified it enough to get it to fit into the action all right, but now I'll need to make a custom buttstock for it.  Don't ask. 

Furthermore:  The damage to the 44 fly, of which I posted a photo a while back comes from it hitting the side of the tang. In this latest exercise I noticed the rub mark there.  If I do build this 44 DST action back into a rifle, I'm going to do as I just recommended - buy a hammer from CPA with the centrally-mounted fly. 

I ordered and received the 44 1/2 hammer and fly. I have to make modifications to make it work. I need to know how the fly is supposed to be oriented. Anybody have pictures?