Your questions are right in line with the questions I was having in my mind. 

On the Woodie Hindeman boat I did I actually deviated from the instructions in the book - used a timber strong back and took some of the rocker out of the little 14' boat in RF book.  I thought the of developing the design of new boat with temp. frames let into strong back, also temp attach stems to strong back.  This would serve as my form for clamping steamed chines and gunnels.  The side pannels would be attached to chines and int. gunnels via ss screws and 5200.  Sides and int. chines faired to accept bottom, 5/8 pannel screw and 5200 to chines and sides, 1/4 oiled skid shoe screwed and poly sulfide adheared to bottom and screwed to int chine.  Ext chines-5/4 with metal band (any ideas on this one) poly sulfide and screwed to sides and int. chine.

I like your idea of a curved bow stem support, seems like deck and rear transom seat would give stability as well.  If more bottom support is needed thinking about  2 frame member under rowing seat  that would work into cross tie(rowing seat support).

Its all in the head at this point, I am just striving to get a clean interior with some nice visable joinery.  I love the looks of the traditional framed boats, but like the functionality of the SG interiors.

Thanks again Rick for your comments- Best, Doug