Looking very, very nice so far. I especially like the scenery work, (catwalks, station....), that your doing there. You definately need some patience to do them the at the standard i can see here. I think, however, that you should leave the terrain flat and just alter it in places that need doing so, instead of having hills and mountains. And also, from my knowledge of dive machines (which isnt huge), the first drop should not have a completely straight section. It should have a very long lead-in (?) that only becomes 90 degrees at the last minute. If you look at this picture you will know what i mean :
http://rcdb.com/2662.htm?p=11839
There is never a straight section on the drop, and if you look at the first two track pieces, you will see that they are both still gradually getting steeper and steeper, and there is olny a moment of full 90 degrees.
Not 100 percent sure if what i have said here is true, but from what i have seen from pictures and in person, there is never a fully straightened out section of track during the first drop.
Apart from that, its looking great!