Two suggestions I have for your UFO route:
As you get around the end of Stage 5, start chaining green UFOs for survival (if you aren't already). The reason for this is that Stage 6 begins with three green UFOs, and you want to exit Stage 5 with green UFOs in stock so as to not let UFOs go to waste.
In Stage 6, if you have two or or three life fragments (in other words, enough that one more red UFO is enough for an extra life), try chaining a red UFO, otherwise, chain greens for the rest of the game. In my first 1cc, I made a futile attempt trying to chain red UFOs during Stage 6. I entered the stage with 0 life fragments, and failed to score another life in this manner. I cleared the game hanging by a thread with a stock of .75 lives and .66 bombs, where if I'd spent the stage chaining green, I would have theoretically ended with 0.00 lives and 2.33 bombs. 2 bombs can easily be the difference between success and failure. Had I been playing any worse that day, I would probably have failed the 1cc, looked back at the replay, and slapped myself for trying to chain red UFOs there.