ranking no.1 in google. doesn't relates to yahoo as both of them have different database server so it is impossible to get no.1 in yahoo if you get in google . similalry algorith to search is totally different in yahoo and google. so,. you need to study well to rank in yahoo.
I don't get this Yahoo SE.... First of all, they don't even highly rate websites listed in their OWN directory. Then, one page sales sites get to rank in first page of Yahoo...you know those sales letter pages... Finally, if you're doing well with Google, they seem to penalize you in a way, unless you're big like Wikipedia. Seems to me their algorithm is designed to be at odds with Google.
I have also struggled getting picked up by yahoo in past. I guess keep working on yahoo and let us know how you get on