OC this system of mine is still under test..if there are 3 qualifying races I select only the spotted horse from the SF and F selections...which result in half the doubles. I play 3 multiple doubles and 1 tripple if 3 qualifying races or 6 doubles, 4 tripples and 1 EW 4 fold if 4 qualifying races. The idea behind it is that the spotted horse have a faster TS.
I only have done it twice in the last 2 weeks..the first time all 4 horse won..which was a nice bonus!! Today I missed the 2.00 at Cheltenham and used only 3 races..2 of the 3 won ...double approximately 15/1.
I still use the same selection criteria that you use. If only 2 qualifying races I follow your system.
“Not everything that counts can be counted,
and not everything that can be counted counts."
Albert Einstein