Peter,
I have a few map pins, in my pin board, and I have seen them used but it never crossed my mind to try them. Now I will definitely try them before ordering a shipment.
Trevor,
Thanks for positive comment. I do prefer to use masking tape and I have found exactly the same problem on wet balsa so I tried Sparky tape which works if you can wrap it around so it sticks to itself. Unfortunately I have run out of masking tape and I am reluctant to go shopping because of the virus risk.
Thanks
The next step is to glue it in place.
Cheers
Steve