Robert,
I'm glad to see you figured out how to attach your SCARM file and download mine. Thank you for that.
I didn't play with it, but it looks like we would have had a bit of a hard time getting things to line up, though I'm sure we could have gotten there eventually. However, there are some problems. One is how small the oval would have been, about half as large as my version. Another is where the purple tracks cross over the lower tracks. Like the green tracks, the purple tracks have to rise to full height before they cross any lower tracks. Fortunately, there are enough purple tracks to do so. Yet another is you didn't include the 2nd crossover I added on the bottom. If you trace your design with a finger, you should see that when you come out of the upper loop, you'll be going counterclockwise and there is no way to get back in to the upper loop without backing up. You need that 2nd crossover somewhere and I don't see anywhere else it will fit.
That said, I haven't asked how finite the dimensions are for your space. My version is slightly deeper because of the crossover on the bottom, but even your version comes too close to the edge if this layout is going on a table of some sort.
Regarding trestles, the last time I used a trestle set was the mid-70s for HO, and I didn't use it long, so I don't have any real experience. Of the 2 sets I found, the MTH set consists of 12 pair of piers making for a 6.5" rise with a 4.7% grade, assuming piers are assembled according to directions and not spread out more. The Lionel set consists of 11 pair of piers for a 5.5" rise, not sure of the grade, but I assume it's close to, if not the same, 4.7%. The MTH piers have a solid wall look whereas the Lionel piers have an open-timber look. Depending on where you buy, price might also be a factor and you'll only be using half the set, but paying for the whole set. Have you thought about making your own piers? Or using a foam product like this from Woodland Scenics?
A rise of 5.5" is okay for most equipment, though I think cars like double-stacks may not clear. Since you're going to use a trestle set, I'm assuming the track will rest on the piers without any further support of roadbed. Since the MTH set has 12 piers, I assume you can simply skip one if you want to lower the height from 6.5". As far as I can see, there is room for the either set, so it's up to you.
Both recommend placing the piers on joints, so that's 11-12 tracks depending on set. It also means the 30" track in the grade should be replaced with 10" straights so the piers can be spaced properly. I don't know what it says about curves or where there are small fitter pieces in the grade. Trestle sets are generally designed for simple grades using 10" straight tracks for the entire grade. Most folks here build ramps with plywood, etc., so I haven't read too much info on trestle sets. Most folks also try to limit their grades to less than 3% and most try to get closer to 2%. Obviously, your design doesn't allow for that, so you're going to have to deal with the steepness, especially when the trains are going downhill. All this really means is you may have to control the speed depending on how well your engines work.
And finally, I'm not satisfied with the "S" curve where the grade begins or how close that track is to the track further out, so I'm playing with that. I also hope you know you used a bunch of different model switches of the same size, manual vs remote, etc.
And that brings up another problem with FasTrack. O72 and O60 switches require 1 3/8" fitters (the hRB versions in the library) that have part of the roadbed cut off, but SCARM lets you connect without them, so that's going to change some fitment when I fix them.