So I've been doing some practice on this and while doing I found a small timesaver in the Monument Island Gateway chapter. Not sure if those are already known.
After pulling the lever that makes the cargo move forward during the Skyline section you can jump in front of it. That's already known (not sure if that saves time). However, if you manage to jump off in a way that you will be really close to it when you hit back onto the Skyline you can get a boost that makes you get to the end of that Skyline in like a second. You do have to spam Space in order to jump onto the Freight Hook as soon as possible otherwise you will get stuck in the cargo that hangs there and you have to switch direction to get unstuck. Also if you jump into the moving cargo you also get stuck and have to switch direction. I've been getting it somewhat consistent and I almost never get stuck so this is something trying to go for is worth it.
e: Here's a video showing it off.
The second thing I noticed is that if you throw a Devils Kiss Trap at a specific point of the guardrail of the airship while riding the elevator up the two guards inside won't spawn. After some more testing I just did this seems really inconsistent. I have had it work every time on one reset from checkpoint, but after reloading the entire chapter it only worked once. Sometimes it works and sometimes it doesn't. Here is a screenshot of where I try placing it, and since it does kill the female guard it doesn't hurt trying to go for this either.
After pulling the lever that makes the cargo move forward during the Skyline section you can jump in front of it. That's already known (not sure if that saves time). However, if you manage to jump off in a way that you will be really close to it when you hit back onto the Skyline you can get a boost that makes you get to the end of that Skyline in like a second. You do have to spam Space in order to jump onto the Freight Hook as soon as possible otherwise you will get stuck in the cargo that hangs there and you have to switch direction to get unstuck. Also if you jump into the moving cargo you also get stuck and have to switch direction. I've been getting it somewhat consistent and I almost never get stuck so this is something trying to go for is worth it.
e: Here's a video showing it off.
The second thing I noticed is that if you throw a Devils Kiss Trap at a specific point of the guardrail of the airship while riding the elevator up the two guards inside won't spawn. After some more testing I just did this seems really inconsistent. I have had it work every time on one reset from checkpoint, but after reloading the entire chapter it only worked once. Sometimes it works and sometimes it doesn't. Here is a screenshot of where I try placing it, and since it does kill the female guard it doesn't hurt trying to go for this either.