Starting at 1, I managed to get up to 18. Had a bunch of lives stored but lost practically all on that level. I've found it's the hardest one.
I did a "special" version where you could reduce it to half-speed by holding the fire button. It was a bit kludge-o-matic, had a nasty flicker, plus I think making something too easy means you just finish it and don't bother playing much again.
Edited by Rybags, Fri Dec 17, 2010 10:53 AM.