Great Pen, John.
Ingenious use of a Specialty Cork.
Your soldering is improving, have you tried sweating the joint?.
That is applying just a minimum cover on the object being attached, and only flux, on the base, then placing the attachment into position, and heating, so that the solder on the attaching part adhere's both together.
That way avoiding the "Puddle Effect".
Love what you are doing.
Congratulations,
Brian.