I was wondering if there was a checkpoint milking trick for Stage 7. I didn't die in Stage 6 so I missed that one. Definitely puts a damper on plans to play the game for score (first loop anyway).
Edit: Also, the game gets rather more amusing from Stage 7 onward (though the play style doesn't really change). After Stage 7 the game starts to break up into shorter segments with short bosses and other stuff up to the end of the game.
Also, letter N on the keyboard changes the direction of the options' shots (first up and down, then backwards; third press returns them to front and center). I got good enough in the first loop to play most of the game without switching, but it really simplifies things. Seems to be a must-have for the second loop, and very useful in loop one's seventh stage.