I finally had a chance to play this game for an extended period.
Solo mode, while actively managing both ships: 223,086 (reached around Level 22)
Solo mode, while playing only as the red ship: 1,810,774 (reached Level 88)
Trying to play as both ships is quite the multitasking adventure. Talk about high stress levels. If you switch to playing only as one ship, you're certain to perform better, despite losing all your reserve lives to repeated deaths of the other ship. This is because it's generally not too difficult to avoid enemy fire if you only need to focus on one ship. Even without the "dual" action, the game is still pretty fun; the multiple enemy types and their various level formations, combined with some very useful power-ups, make it almost play like a puzzle game. Watch out for that skew-reversal power-up when playing this way, though, as you might suddenly find a cloud of enemy fire coming at you from close range. . . .
LJ guys, I lost my last life in Level 88 when a mothership plowed into me. Is this a bug? There was no way to shoot that ship because it was approaching me from the side, so it was a foregone conclusion (literally!) what was going to happen when it appeared on the screen, in line with my ship. I wanted to see the 5-hit enemies, too. :(
By the way, I noticed your "KAYTHXBYE" in the default high scores, but what are the other initials supposed to be? They don't seem to be your initials.
Also, the way the music changes is funky.
I definitely need to sample the two-player modes.