More rant from the bat people. Sorry for laying our eggs on your cedar branch but it's the only way to post comments with the pics.

So, rear stem.
The smaller side tubes slide into the larger alu stringers of the rest of the boat. They fit to the light okoume stem piece at an angle thru perforated steel fittings that were bent by hand to match the hull beam, and washers to relieve their tearing into the wood.
Normally such interior tubes are riveted to the stringers, but that variation permits faster assembly: the curve of the stringers reduces their sliding along, also they are long narrow though thick dural tubing, and they're kept within the skin anyway.
Also, I thought it would add some flex to a structure that was lacking some because of the absence of beveling of the crampons' inside faces.
Actually I can't confirm this for the moment as such moves are uneasy to observe on a hull at sea.
By the way, such 2mm thick tubes require upicking a different, longer kind of rivets because of their steeper curve.
The T-shaped steel (four on each stem) fittings should be made of dural rather, but due to ordering delays I clicked the Yeehaw button not to waste too much building time. Those are most cheap and easy to come by, anyway. A few coats of varnish give them that miserable yellowish color.
Four black PVC caps were fitted to the top and bottom tube ends in order to prevent their edges cutting the wood stem piece top and bottom ends.

Like a good weekend Inuit I had sewn the deck to the bottom before gluing, but as this resulted in an extra taut skin I had to shorten one of the stems so that the structure would fit better into the skin ensuring easy assembly.
I just had to saw a 1/4" wide strip off the rear edge!