I have known a few friends who do Cheng Manqing's form and when I changed (actually got rid of what appeared to be 'limp' look postures) they felt at least 100% better in doing the from.
I didn't change the form per se but I picked a stance for them between high and medium (all relative here), then I added more(allowed for more kua/yao rotation (mingmen/shenshu involvement (lumbar (left/right rotation) extension of hands to about 80% with wrist flexion between 20-40%, and actual raising of the knee (as in repulse monkey between 45-85% in execution (90 degrees=%). Footsanyang, through taijiquan practice is bettered when there is empty/full (xu/shi) awareness and it help with balance problems when done correctly!