I was about to say something similar. I mean that the primary hull is indeed reminiscent of many later primary hull designs, and may be chronologically one of the first to use this hull shape for the primary hull (though there are of TOS-era vessels that does have a primary hull with a similar shape, such as the Fast Dreadnought). While the shape of the front of the secondary hull and placement of the navigational deflector is reminiscent of the placement on the Intrepid-class.
It will be interesting to see where you will place the phaser emitters and torpedo tubes, assuming you intend to make them visible, since not every designer makes the weapons visible of ships of this era.
The Hecla has some nice design elements, and her primary hull makes her look faster than her Saladin or Larson-class Destroyer contemporaries.