Graham,
I don't know what to say... I literally speechles... Thank you for your praise and kind words... (You too, Rick und Mathias).
And Graham you're too giving something to this community with your budget tips.
I am just happy to have helped you! Your hanguards look great!
And I even have a great solution for you:
As you said, your guardfs a little to big: Connsider them your new master tools!
You should have no problems geting them out of the plaster, you don't even need an release agent.!
To solve the missing top layer: dremel or carve or groove to simulate the top layer, or - even better - bush several thin layers of latex on top of it! (don't forget to mask)