One thing I've found that's helpful on Canyon tracks to reduce DC is to use the blocks that have no support pillars, especially if you're using a bunch of them in the air as a driving surface, since although you won't ever see the pillars, the game still has to take them into account when rendering frames.
I also found that making terrain blocks have straight rear edges helps a bit, too (see picture below) – again, although you won't see them when driving (unless you go far off course) the game still has to deal with them. The change might not be much, but lots of them together can certainly add up
(this applies to Valley, as well)
Another things with terrain is that the 'decoration' blocks (to make the edges of canyons/cliffs more varied) also add to the DC, so you could remove them where they're unlikely to be seen.
Last edited by caerphoto,