Here are some interesting things usign DS ratings and R&S.

If you bet the DS highest rating selection you lose 16% on unitab.

If you bet any horse that were priced higher then the rated price you lose 20%.
If you bet any horse that are at least double overlays you get a los of 18%.

If you took the highest DS Rating selection and those that were overlays you get a 15% loss.

All figures are unitab.

The DS Rating system obviously needs some filters for it to be proftiable.