Damn. That's harsh.
Where do I start? I understand the length problem, though, if I was to decide, I would prefer to get rid of the first half. It doesn't have anything to do with Science and it could be used somewhere else if a level needs to be lengthened or I could start a personal romhack and recycle it that way. I would have liked to know about the music. I spend a whole day figuring MML editing in-depth and composing the song. I'm not really complaining since it can also be used for something else, but more info in the op would have been nice.
If I was to keep the middle sublevel to retain a part of the pursuit idea and double/triple the last area, would that be a good length? The only other Sibling hall I have seen and played is Cup's and it is 21 screens long and fairly hard. My second half currently has barely 4 screens, although screen number is probably not a good indication alone. I would also say that my first half is way easier than Cup's level, but it doesn't matter if I remove it anyway. You have a point that it's a pain to replay it every time to get to the hard part. That's another reason why I want to get rid of it.
About improving the second area, I don't have the knowledge and time to learn how to modify the game physics. I can maybe succeed with the gear's hitbox, but that's already quite a lot time-wise. There is no reason not to use the propeller btw. One thing I could do would be to give the propeller at the beginning to make this clearer, move the two sections I have made higher, make an easier part at the beginning to give the player some time to learn the gimmick and space the gears in the zigzagy tunnel. That is something I could do and I think that the added practice space, plus respawning right there after dying should be sufficient to make this easy enough.
I have also made this test with goo (tile 403) instead of water.
http://dl.dropbox.com/u/4676540/smw/Sci ... 20test.ips
I like it less and it doesn't work with slanted ceilings, but you get more control and it works well with the horizontal tunnels. Maybe if whoever made the goo block could make one with half the effect? I would prefer to keep the water though and make the changes I just said if it's alright with you.
So, what do you think?