Found a very fast setup for the Wave + Sun IS that's equally simple, and very consistent from my experience with it.
Skip to ~1:50 for the setup.
All you do is line up with the vertex of the alcove with the bomb slot as shown in the video, morph, and hold directly Left and you should start spinning up for Infinite Speed. The only stipulation is that you have to bomb yourself before boosting twice. For some reason unbeknownst to me, this only works if you bomb yourself. Simply boosting will lead to nothing happening (at least in my experience).
If for some reason directly Left doesn't work, the angle should be very very close so just wiggle around and you should find it. I only had one attempt out of ten where I had to actually search for the angle, and that was because I rushed the setup.
EDIT: Does anyone have any insight as to WHY it only works if you bomb first? If you use this exact same setup and only boost, nothing will happen. This only works if you place a bomb and then boost twice. I suppose it's not really important as long as it works, but I'm really interested because of how strange it is.
I recently learned something about half-pipes that is probably known by some people, but I figured I'd share it anyway for those who aren't in the know because it's really useful to know for some rooms.
I was messing with Life Grove Tunnel for practice and whatnot, and learned what causes it to randomly kill your speed. Basically, if you hold any direction other than Left or Right while rolling in the half-pipe (such as UpLeft, UpRight, etc etc) it will probably kill your speed. If you only hold either directly Left or Right, your speed shouldn't get garbled ever.
I've figured that this happens because, when you hold any direction other than Left/Right, the game interprets this as wanting to either 1) Move somewhere else on the half-pipe, or 2) Wanting to leave the half-pipe entirely. Since Life Grove Tunnel is only as wide as the morph ball, tapping any direction other than Left/Right while riding it results in the game either rubbing you into the collision holding you in the tunnel, thus killing your speed, or simply stopping you because it thinks you want to move somewhere else.
This can also be used to make getting out of this (or any other) half-pipe a lot easier too. If you simply tap UpRight, UpLeft, etc. when you want to leave the half-pipe, the game will allow you to leave.
Possibly faster with better execution? I waste a lot of time needlessly turning the camera and my execution is meh. I'm also confident the dash done OOB can be done better but this was the best I could get when messing with it.
The first dash is a pain in the ass but the one done OOB is easier than it looks.
The first dash can be made a lot easier at the cost of ~1 second by instead jumping up to the ledge above your head (where the missile expansion is) and dashing from there instead.
Not as scary as it looks. Saves a bit of time over jumping on top of the morph ball section.
EDIT 2 - Found yet another optimization
Saves like 1-1.5 seconds but requires doing a single aether jump.
EDIT 3 - I'm on a roll today
This should hit the load trigger sooner from what I understand. Probably only worth it for segmented if so because of how annoying that first jump can be due to all the stupid collision around the door.
EDIT 4 - last one, I promise
Probably faster than what is done right now but the bomb jump is extremely obnoxious so it'd probably only be worth it in a segmented run.
yeah it really is fun :) and it is of use in many places and theoretically in waaay more places than most of us use on a regular basis. i mean TASing those will save so many seconds across the whole speedrun it's crazy! What i think is even more crazy than how dash hopping saves time is how that weird R-jumping that accumulates speed (if done properly/ (almost?) frame perfectly): i just can't figure out myself how to do those. anyone has recorded/ can link a non-TAS video of those R-jumps I'm talking about?
Note: the dash doesn't need to be done from atop the rock I was standing on in the video. It just gives you a convenient slight boost to your starting height for the dash.
EDIT -
The first dash I showed puts you in perfect position to do this afterward.
EDIT 2 -
Or this.
Why did I make the effort to make an already terrible room even worse?