nice game. I think all maps that are used in an "event" should be playable as "single race".
Every time i want to practice the old mcdonald map i have to play all the other maps first. And after 3 trials i have to start over. I'm not such a good Player and so its exhausting. And all the other maps of that event i can succeed without any problems.
hope you find time to go on with developing
That's easy (with symbolic links). I did here (Xubuntu 9.10) and you might try
at yours. You can do with each map from triggercup to have them on single
$ cd /usr/share/games/trigger-rally/maps
$ sudo ln -sf ../events/triggercup/warmup