Well earlier today I found a way to get on top of the roof of the Lumber Mills building in Arathi Basin. All that is require is Rocket Boots and Slow Fall. I haven't tried any type of slower item than Rocket Boots but feel free to give it a try and respond.
1. I am right to the right of the building if just leaving the graveyard.
2. Jump onto the saw and walk to the end of it.
3. Look to your right and hop down onto the tree limb.
4. Look to your right again and hop onto the next tree limb and hop down onto it.
5. Mount up at the end of the tree limb and jump over to the hill.
6. Walk around to the the small hump in the ground.
7. Here is the strange part, I know wall jumping was removed in 2.4. Yet when I went to jump around the edge the clipping is in the correct areas to kind of wall jump. Do this on your mount.
8. Once you make the jump walk around the curve until overlooking the building.
9. At this point activate your speed increasing device and slow fall and jump in the direction of the building.
10. This is the way you should jump across.
11. Once you have done all of the previous you will achieve this finished project.
Well I couldn't find any type of that in the other posts so I guess this is new. Have fun with this and if anyone finds an alternative way to get enough speed with the slowfall to make it feel free to tell me.