"A good fit" means that it must be fit the person's body and status, whereas "suiting the posture" means that it must allow the body's four limbs to move without being constrained. Hence, "Although making a ch'i-p'ao is not hard, making a good one is not easy."
「合身」是指合乎身材、身分；「適體」是適合體態，穿在身上四肢運用自如、沒有束縛感，所以「做旗袍不難，要做得好卻很不容易。」