Hi Kevin,Thanks for that.
Answers below.

) [/iWhat causes friction of the skeg to hold position, up/down/middle?
A. The loop of cord is tied fairly tight,enough ,at least, to need the knob on the side that would need to be pulled back to release tension.This then in turn allows the pulling direction cord to displace the skeg.I didn't think about this possibility but the solution was easy to find.

2) How do access the rear of the skeg box for maintenance of the control lines and components?
A . As you may see I have not cut the hatch holes yet ,mainly because I want to go paddling after a year's worth of boat building.But I "must do the hatches in this case in order to beable to reach that back ferrule and make sure the cord goes through it and through the one on the shear clamp.i have also got a fair bit extra cord [3 meters]in the loop.

3) On the rear port ferrell, could you have used a pulley here to reduce wear, or does this cause the friction of the skeg blade to hold position?
A. The friction is just an acumulation in all the tension points adding up in each direction the cord is pulled.The tension jumps up each time the cord goes through a ferrule accumulating in tension in the direction up to the pulling point.When I hit the skeg imitating a rock The skeg moves enough to releive some of the shock .fairly easily,however at the actuation end [the balls the friction accumulates in bothe cords so they bothe need some antitension as it wher to allow them to move.This cord system is what is locked up.
A pulley sends the solution into the complexity where the cord run may malfunction.The friction is not high,just enough for me not to need an additional friction device

4) Do you have close up of the back of the skeg box to further understand the waterproof seal of the line through a tube?