Dont u worry Just try it out, in fact only I have obtained 2 shinies since this challenge started. The other ones (as far as I know lol) have found none yet themself. So you arent behind at all lol. Id say just give it a shot, see what you think. I do one know one thing though, and that is you will ALWAYS get a shiny if you keep on going. Might take you even 10000 random encounters or SR's, but you will get it.
I hope you'll take this challenge and good luck to you if you do so.