Maybe this is where a good handicapper comes into play. Why not a race for the Rating 80 horses with $ This Season less than x. May not be a full field of 12, but perhaps a race with 7-8 horse all being a live chance would be a better betting proposition than plonking them back in the Rating 60 category as $1.10 shot.
As much as they think they police it, trainers are not immune to winning a race then after 4 or 5 unsuccessful runs, going around another half dozen times quietly, or dead for the usual term, to get the drop back. Isn't any inconvenience when you have a few horses, you're already going, so why not take 1 dead one with you as well.
The stewards are probably aware of it, but proving it is another matter. I was informed early on in my career that there were many ways of getting beaten without causing alarm.