I'm thinking the Penguin Suit could be a big help on 9-7, much like how the Propeller suit pretty much broke 9-1. Though from my limited experience with trying 9-7, it does seem like momentum is important. The longer you wait, the more precarious your position becomes.
I had to rely on pure luck to get some of those world 7 coins. 2nd coin on 7-3 i found by randomly jumping and finding the invisible block that spawns the vine that goes up to where the coin is, and the 3rd coin in 7's Ghost House i really agonized over, because i was unaware the level had a hidden exit, and i happened to see the boxing ghost punch through what appeared to be solid wall at a point
2nd coin in Ludwig's castle was bad, too. Hiding it under a warp-pipe that was itself hidden in the cloudy fringes was devious of them
Monster Hunter: pissing me off since 2010.
