I think the amount of overlap (bury) is 30cm and therefore within the approximate 10% which is regarded as a minimum for tabernacles, so in theory the join itself should be as strong as the rest of the mast, in bending. However there is still the problem that the halyard and yard will put a rotational force on the top of the mast. It would be interesting if the top section of the mast was able to rotate. I have never heard of that being done, (though I have seen on other more simple rigs, rotating masts where the entire mast is allowed to rotate in the partner.) I suspect that with all the running rigging which is usually carried on a junk mast that rotation of the top part would be unacceptable, but I don't know from experience. Maybe the top part, if not glued, would need to be secured in some way so as to prevent rotation, but I am not sure the best way for a carbon fibre tube. Hopefully someone else who knows more than me will chime in here.
I had a sailing dinghy a few years ago, in which the mast came apart simply, in two parts. It was no problem, quite convenient in fact, but it was a very simple sail.
My own thought would be to glue the mast fully and just accept that when trailing the boat, the mast will need to be carried over the top of the cabin and will protrude forwards and aft, a little, which is the usual way for a trailer sailer. However there is room for some other ideas here. Your little boat is very interesting and when you get her sailing, some more photographs and a description would be very good.