If you start with only 5 lives and must go through 11 levels
of harsh battle, I don't think you'll make it, unless you are
lucky and fast enough to get extra lives. But you can save
your game, and use a hex editor with the save game to change
the byte at offset 5(hex) to 05. This will return you to 5
lives.
I tried fixing it with FF, but I found out that it doesn't
work - I lose as if I had no lives left. You can attempt to
screw around with other bytes and hopefully get more lives
than five.