3 simple words... Get the demo.
^ As for you, Dirk, just use custom structures.
IMO, RCT3 is fun when you start with all these new features, but the basics of the game iteslf was done poorly. For example, the scenery placement is extremely tedious, it takes like 10 mins to make a station when it only took about 2 mins in RCT2. They took away custom support objects when you expect them to add more, and the coasters are still their crappy old selves, and they have no excuse for that since it's now 3d. Even a simple track scaling system would be nice. And though minor, they should've made the overbanks correctly and not place them on B&M's (that was just weird). And the 0 g rolls are on the vekomas and arrows, not the B&M's, which is just plain retarded.
But get the demo first.