You are correct Arrow5. I'm using 3.6 mm and it's quite stiff.
Have succeeded with the clamping and now have two new Springers.
Dan,
I have two boats from Bosun, delivered today. I have taken some snaps to whet your appetite. Please see pictures below, as one has a motor and servo and rudder, and the other is a Pusher tug of larger dimensions with no innards, so you should be well on your way. Do you still need one of mine, or can I make something for myself?
ken