As it turns out, as I wrote my last post, the seat post clamps I needed to finish the stabilizer mounts were sitting on our front porch. I was able to add these to the arms yesterday. I needed to file about 1 mm of material off of the tube to leave space for the lip on the inside of the clamp. This usually serves to keep the clamp from slipping down the seat tube. Here it also helps keep it in the correct position. I also drilled a small stress relief hole opposite the 3/8" snap button hole and used a hacksaw to create a slot about 1 inch long up to the small hole.
I got the clamps in position and I would say they work well. They will keep the parts from moving with regular motion of waves, but they can still be moved since the lever arms are so long. With the weight of the clamps, the full assembly is pushing 13 lbs, but there is no extra stuff on the hull except for thread inserts.
After getting the full assembly together, I became a little concerned that my last minute change to allow split mounting and independent height adjustments might have compromised the strength more than I expected. The photo here shows the two halves joined together. There are a series of holes 3/8" apart to allow about 1 1/2" of movement in each direction. I guess if I had planned ahead and knew the direction of prop rotation I really would have only needed to adjust in one direction, but there was enough space for both.
The two halves create a "V" that will nest with the fairing on the seat back. The long slots will allow overall height adjustment with 4 knobs threaded into thread inserts in the seat back. Now that the full assembly is together I have a better appreciation of two things. First, the stabilizers are a little heavier than I was expecting at 5 lbs each. This doesn't seem like a lot considering I used a minimum of epoxy and glass, but the second thing I have a better appreciation for is the feel of hanging 5 lbs on the end of a 3 ft lever arm. It would have been an easy calculation, but I admit it wasn't something that jumped out at me having never used a boat with outriggers before. Needless to say now, the long lever arm causes the bracket to flex quite a bit at the two fasteners holding the halves together. Fortunately, I did fiberglass inside and out of both bracket halves so the panel joints will be secure. This flexing should be improved a bit when there are 4 extra fasteners holding everything to the hull, but it could still be an issue. I guess worst case, once I arrive at the offset I would like, I can re-glue the halves together permanently in this position. I'll have to try it to see.
Overall, I like the ease of folding the stabilizers up behind the seat. I am hoping that I can also raise the bracket high enough to put the stabilizers on top of the rear deck, otherwise they will hit the sides a little and I will need to bungee them in place so things don't bump around. With the 4 fastener knobs holding the whole thing on, if I do need to cartop the boat, I can easily remove this weight and save my back when I lift the 55+ lbs I expect the rest of the boat to weigh.
Time to this point (everything including repeating steps): 120 hours