Howdy Bill,
Thanks for stopping by. Not really concerned about the motor bearing strength of the transom as overall rigidity. Now most of the folks who mention that in the reading I have done are associated with the modified PDR and are trying to sail fast enough to get on plane. The other thing they muse over is the strength of the bow and how the forces of sailing put pressure on those joints.
My brick is intended to be a slow moving Men's Bass Boat ( M.B.B. as opposed to the ones by fishing buddies pilot with the motors and cushioned seats and sparkle paint

) and great nephew transporter. I do want a sail on her, but would consider four knots all the speed i would ever want on a pond. These operators do strange things afloat on our ponds, most of them entirely ignorant of navigation, courtesy, basic physics, and of course my personal favorite, safety.
I have been "hiked out" on a fourteen foot Hobie Cat, a 21' sloop out of Hyannisport, and too many tiny sailfish and sunfish to recall. Not really what I am looking for in this brick. Most of the time, my inflatable kayak will still be my ride as it's always in the trunk unless specifically removed. The brick is for days when I know it's time to fish. If she works out well, an itty bitty sail and perchance a motor. ( of the tiniest stripe, or a Li-ion 2.2 hp torqueedo if finances allow)
Cut the stern transom a wee bit short and put some ripped 1x2 on it which makes it a bunch stiffer, the boat is plenty light without glass, fillet, and paint. The seating boards and gunwales I am envisioning would add weight and I have sat and pondered those same thoughts. My inflatable is the "go to girl" when I know there is a portage, but the kayak design has it's limits especially in comfort over a long day. To the basic hull, I want to add 6 2x4x8' boards. That's a bunch of weight, so I flip the mental coin back and fourth......
My thinking is that if she has some of the strength to make a good racing/sailor she will do what I want her to do long after I have returned to port. If I can beef her up just a tad but still manage to get her on and off the luggage rack I am gonna call that success.