Update: Layout has been successfully designed, and after many failed element sequences in between both the other collisions I wanted work beautifully. Next step, re doing all the track work to a better standard now I know the layout is plausible.
The timing on the final collision is still about 0.1s off, but that can easily be fixed with a few hours of tweaking which isn't worth doing on a first draft. So I'll keep that one as a surprise for later. [;)]
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