A quick thought about pants alterations.
Generally when you ask a tailor to taper a pair of trousers, he/she will start from the knee to arrive at the desired measure at the hem.
Example (measurements laid flat)
- initial: 20cm at the knee, 18cm at the hem
- measurment required: 17cm at the hem. So he will start from the knee: (20cm), and reducing the leg opening progressively until 17cm at the hem by "plotting" a straight line from 20 to 17cm across the leg. So...