clamshell catches

[ProtoTipo]

Good info. I was about to start on these myself. What diameter are they?

5mm OD

For the two longer pins, 30mm is a tiny bit too short, 40mm is too long. Something like these might do:
http://www.ebay.co.uk/itm/5mm-CHICAG...tpc36-t7uYMIGw