I think I would make the tail of one piece. I've shown it attached in back just under the point where the back of the skull is more or less straight. This put more of the burden on templating and less on subsequent shaping. Alternatively, the tail seam could be made lower. That would divide the back raising between the tail and the side plates. It's six of one and a half dozen of the other. In any case, the forward end of the tail seam is well below the "corner" of the facial opening, and ends in points. This all reduces the stress concentration on the weld. The points get removed when the hammering is done.
Likewise I would put a point on seam in the middle of the brow. I've shown that in the front view, but forgot to include it in the side view.
My front view is a bit "tighter" at the bottom than yours. It's probably easier to flare the lower edge than to back raise. This is just personal preference. Either way will work.
I've also allowed for a bit of sinking in the middles of the upper panels. Again, this it just personal preference, but I think it distributes the work better.
I like to try to get as much of the profile of the front to be "baked into" the design as possible. It can be difficult to reshape a welded crestline, so I try not to need to.
I hope this is helpful.
Mac
