As you (and others here) might have guessed my knowledge of building and fulcrums and such like is very, very limited – I never got beyond a basic Meccano kit and a Lego starters pack, and yes that was all a long, long time ago. :)
Anyway, thanks for the feedback – especially the physics bits (which I think I’ve grasped).
I’m now waiting for Scott’s response to your comments and observations.
So few answers - and not one of them mine.