If you use heat-activated hem tape to secure the cut-off edge of the jacket
Do not use this! You can ruin the fabric by the heat required to apply this, as well as run into bubbling of the fabric.

Get yourself a pile of pins, make sure that they are not ball-point or poor quality pins. Invest in some nice hand-sewing needles and basting thread. Read the sticky, post here with pictures and questions.

Good Luck!