how much activity in the plantarflexors? i can't imagine a hemiplegic with plantarflexors activating and NOT the quads... there's gotta be SOME quads... if you can get the patient in to standing with assistance, increasing the proprioceptive input through the knee might increase activation of the quads...

if you can paint us a better picture of what that lower extremity looks like (as well as the non-affected LE) i might be able to offer more specific ideas...