After seeing Matty's Cyclone re-creation in his thread, I noticed he made custom supports. How do you do that?

I believe they are actually walls, but yeah. They look like the wall/windows in RCT2.

For the custom supports on cyclone I used one of the walls in the generic building grouping near the bottom of the list I think near the base blocks. I just got these and placed them one on top of each other until they got to the top, and if they didn't reach I would usually go to the adjacent grid square and move the position of the wall right to the top so that it overlaps the other wall pieces and brings the customs supports right up to the track. I thought they were much more realistic for cyclone supports around the lift hill and first drop then the steel supports (and I think it worked out well). And yes that wall piece was a wall that was also in RCT2 as well. Unfortunately not all of the supports in RCT2 are back in number three (they were good for wooden coasters). You may have noticed I also used the same wall piece in my Cedar Point Recreation to enclose the tower of Demon Drop to make it more realistic.