...Since your giving out advice, do the levels after 10 get even hard?
As you may have noticed there is a bird after 5th one, but nothing changes after 10th. Although I think thugs might be faster and more aggressive. Basically what happened I managed to survive with all guys till the 5th level and then I started loosing them at about guy per level, that's why I got to 11th.
Let me address some other issue I've missed though...
I only recall seeing Bosconian at the local Chuck E. Cheese. It was a clunky game, even for '81. Goes to show Namco did have B or C grade games during that time.
I'm entering some off topic angry territory, but I still don't get the love affair with Galaga, and there is NO WAY that Bosconian is B or C grade. It's on par if not BETTER than that borefest that is Galaga!
It's not my fault I'm so awesome!
You forgot to mention how humble you are, too. 
But that just proves how truly humble you are. 
Scott
Duh!
I'm not even gonna mention all the grandmas and blind man I help to cross the street, or the countless mine fields I've disarmed! all the little kittens and even little snails I've rescued! I'm not only humble, but also smart, beautiful, awesome, cool... popular... umm awesome, have I mentioned that?