OMG. Just OMG. Wasn't it Saito Morihiro who said you should practice only kihon waza until sandan?
Yup...'cause that is what Osensei always said, too!
They don't have to be big in order to give 'trouble' ... I'm 6'4" 240 lbs and one fellow I train with is ~5' 170 lbs and 70 years old and strong like an ox. Gotta be just right or he is not going to move. I relish those moments because more is learned then than most every other time. Even kinonagare won't be so good if the execution is not just right - no kuzushi=no aikido.