Finding a BGS early entrance would save a lot of time. I'm just throwing out some ideas, but nothing has worked so far
-can the ice cube in fp puzzle (I think you have to enter fp for them to appear) clip you out? I find it interesting that with some rng, you can get one of the ice cubes onto the puzzle ledge. No luck on that ledge either.
-the cheato entrance area? The sides look funny with talon trot, but not getting any clips yet.
EDIT: Another possible area: Talon trot clip here (outside fp puzzle area)?
https://imgur.com/Hd6Yzoh No luck, but I feel like it is harder because of the swamp water.
Also, new idea for spiral mountain. After boulders, roll onto 1st level of mountain and go to stumps (skip underwater honeycomb). do same stuff until after waterfall honeycomb. Use this glitch (it is possible to get ground after 1st diving animation + 1/2 swimming animation)
https://www.youtube.com/watch?feature=player_detailpage&v=KhBl53_b-DQ#t=16. normal jump to resurface and then follow same route. I think it saves like 0.5-1 second, but anyone else can check if it does.
EDIT 2:
No luck with bgs still, but are these crevices graphical bugs, or actual openings?
https://imgur.com/a/XEA7S