There are a couple of these layouts to choose from so I chose yours coz it's more dangerous than the others even though there was one which had better scenery layout I like how you've done the elevation,Take a drive around BrunoPro74 track to get some idea.Cheers
But as afaics Bruno Pro has done the oval alone, without the actual track included!
You should also have a look at his Suzuka-course where he had to cut and lay the track in such a way, that they do not cross each other (which they MUST, otherwise it's not Suzuka... and also Suzuka already exists in GT6 the correct way... I don't know how they do it at PD and don't let us do it in TPE also?).
As far as planting of objects is concerned: I planted as much as I could, but you cannot plant objects everywhere due to some stupid TPE-restrictions (which is especially true in narrow curves and hairpins, where the construction of such curves already is a problem in itself).
I would have loved to plant more objects, believe me, but TPE doesn't let me!