During the lasts months Ive been working like this and didnt have any problem.
Deck set at 59,94.
FCP set at DVCPRO HD 720p 60. With this easy set up you get 59,94 fps secuences.
No matter at wich frame rate the tape was recorded, FCP always undertood the as they where at 59,94. I worked just fine with this method, so I think the problem is somewhere else.