The screen colour filling example in #2 doesn't work on older KERNALs, the screen colours will be set to the contents of $d021 instead of $0286.
When the submissions are put on tape, do they have to follow the same memory rules? It's much, much harder to avoid writing to addresses above $0fff then (or having the file fit below $1000 since we can't easily load from as low as $0120).