Yeah, I tried it again yesterday and it looks like I don't have the faintest chance of ever getting past this guy. I have to admit that I must do it with single raimbows because I find the area before you come to this boss incredibly hard and I always loose lives there. Since I have a trainer now with infinite lives I tried the boss multiple tens of times (with one rainbow of course) but there's absolutely no way
I tried to evade him by climbing up somehow and dropping down when he's close to have enough room at the bottom to run below him to the other side of the screen. But when I#m trying to climb up on the other side and he is spitting his bats the story is over. I don't know how to evade him and defend against his bats at the same time.
I was really pissed after that and tempted to give my arcade/amiga machine a few kicks.