I think that the intensity tolorences of the guests are very realistic. If you design a coaster correctly, the guests will ride it. Usually, the ones that the guests won't ride usually have very high G forces, higher that you would usually find on a real roller coaster. Roller coasters are SUPPOSED to be hard to design, otherwise, the game would be too easy. You can't expect to build every coaster that you see in real life in RCT though, because it doesn't have the right types of track pieces.